tracing/lockdep: Fix dependency of TRACE_IRQFLAGS

When CONFIG_IRQSOFF_TRACER is set and CONFIG_PROVE_LOCKING is not, we
get the following error:

$  make oldconfig
scripts/kconfig/conf --oldconfig arch/x86/Kconfig
warning: (IRQSOFF_TRACER && TRACING_SUPPORT && FTRACE && TRACE_IRQFLAGS_SUPPORT && !ARCH_USES_GETTIMEOFFSET) selects TRACE_IRQFLAGS which has unmet direct dependencies (DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && PROVE_LOCKING)
warning: (IRQSOFF_TRACER && TRACING_SUPPORT && FTRACE && TRACE_IRQFLAGS_SUPPORT && !ARCH_USES_GETTIMEOFFSET) selects TRACE_IRQFLAGS which has unmet direct dependencies (DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && PROVE_LOCKING)

This is because IRQSOFF_TRACER selects TRACE_IRQFLAGS but TRACE_IRQFLAGS
has PROVE_LOCKING as a dependency. This code is incorrect, and
this patch changes the TRACE_IRQFLAGS to be just a simple bool that
does not depend or select anything. Instead both IRQSOFF_TRACER and
PROVE_LOCKING select it.
Reported-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

lib/Kconfig.debug

@@ -482,6 +482,7 @@ config PROVE_LOCKING
 	select DEBUG_SPINLOCK
 	select DEBUG_MUTEXES
 	select DEBUG_LOCK_ALLOC
+	select TRACE_IRQFLAGS
 	default n
 	help
 	 This feature enables the kernel to prove that all locking
@@ -579,11 +580,10 @@ config DEBUG_LOCKDEP
 	  of more runtime overhead.
 
 config TRACE_IRQFLAGS
-	depends on DEBUG_KERNEL
 	bool
-	default y
-	depends on TRACE_IRQFLAGS_SUPPORT
-	depends on PROVE_LOCKING
+	help
+	  Enables hooks to interrupt enabling and disabling for
+	  either tracing or lock debugging.
 
 config DEBUG_SPINLOCK_SLEEP
 	bool "Spinlock debugging: sleep-inside-spinlock checking"