ARM: hw_breakpoint: fix warnings generated by sparse

sparse doesn't like per-cpu accesses such as:

static DEFINE_PER_CPU(struct perf_event *, foo[MAXLEN]);
struct perf_event **bar = __get_cpu_var(foo);

and shouts quite loudly about it:

| warning: incorrect type in assignment (different modifiers)
|    expected struct perf_event **slots
|    got struct perf_event *[noderef] *<noident>

This patch adds casts to these sorts of assignments in hw_breakpoint.c
in order to silence the warnings.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm/kernel/hw_breakpoint.c

@@ -337,7 +337,7 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 		/* Breakpoint */
 		ctrl_base = ARM_BASE_BCR;
 		val_base = ARM_BASE_BVR;
-		slots = __get_cpu_var(bp_on_reg);
+		slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
 		max_slots = core_num_brps;
 		if (info->step_ctrl.enabled) {
 			/* Override the breakpoint data with the step data. */
@@ -357,7 +357,7 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 			ctrl_base = ARM_BASE_WCR;
 			val_base = ARM_BASE_WVR;
 		}
-		slots = __get_cpu_var(wp_on_reg);
+		slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
 		max_slots = core_num_wrps;
 	}
 
@@ -394,7 +394,7 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 	if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 		/* Breakpoint */
 		base = ARM_BASE_BCR;
-		slots = __get_cpu_var(bp_on_reg);
+		slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
 		max_slots = core_num_brps;
 	} else {
 		/* Watchpoint */
@@ -402,7 +402,7 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 			base = ARM_BASE_BCR + core_num_brps;
 		else
 			base = ARM_BASE_WCR;
-		slots = __get_cpu_var(wp_on_reg);
+		slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
 		max_slots = core_num_wrps;
 	}
 
@@ -662,9 +662,11 @@ static void disable_single_step(struct perf_event *bp)
 static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
 {
 	int i;
-	struct perf_event *wp, **slots = __get_cpu_var(wp_on_reg);
+	struct perf_event *wp, **slots;
 	struct arch_hw_breakpoint *info;
 
+	slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+
 	/* Without a disassembler, we can only handle 1 watchpoint. */
 	BUG_ON(core_num_wrps > 1);
 
@@ -703,9 +705,11 @@ static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
 static void watchpoint_single_step_handler(unsigned long pc)
 {
 	int i;
-	struct perf_event *wp, **slots = __get_cpu_var(wp_on_reg);
+	struct perf_event *wp, **slots;
 	struct arch_hw_breakpoint *info;
 
+	slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
+
 	for (i = 0; i < core_num_reserved_brps; ++i) {
 		rcu_read_lock();
 
@@ -734,10 +738,12 @@ static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
 {
 	int i;
 	u32 ctrl_reg, val, addr;
-	struct perf_event *bp, **slots = __get_cpu_var(bp_on_reg);
+	struct perf_event *bp, **slots;
 	struct arch_hw_breakpoint *info;
 	struct arch_hw_breakpoint_ctrl ctrl;
 
+	slots = (struct perf_event **)__get_cpu_var(bp_on_reg);
+
 	/* The exception entry code places the amended lr in the PC. */
 	addr = regs->ARM_pc;