nios2: Add NIOS2_ARCH_REVISION to select between R1 and R2

Allow user to select between Nios2 R1 and R2. Since R1 and R2 are
not binary compatible, we cannot have a single kernel binary and
there is no point in having DT property for discerning these two.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Ley Foon Tan <lftan@altera.com>

arch/nios2/Makefile

@@ -22,7 +22,10 @@ export MMU
 
 LIBGCC         := $(shell $(CC) $(KBUILD_CFLAGS) $(KCFLAGS) -print-libgcc-file-name)
 
+KBUILD_AFLAGS += -march=r$(CONFIG_NIOS2_ARCH_REVISION)
+
 KBUILD_CFLAGS += -pipe -D__linux__ -D__ELF__
+KBUILD_CFLAGS += -march=r$(CONFIG_NIOS2_ARCH_REVISION)
 KBUILD_CFLAGS += $(if $(CONFIG_NIOS2_HW_MUL_SUPPORT),-mhw-mul,-mno-hw-mul)
 KBUILD_CFLAGS += $(if $(CONFIG_NIOS2_HW_MULX_SUPPORT),-mhw-mulx,-mno-hw-mulx)
 KBUILD_CFLAGS += $(if $(CONFIG_NIOS2_HW_DIV_SUPPORT),-mhw-div,-mno-hw-div)

arch/nios2/kernel/cpuinfo.c

@@ -125,12 +125,14 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 
 	seq_printf(m,
 		   "CPU:\t\tNios II/%s\n"
+		   "REV:\t\t%i\n"
 		   "MMU:\t\t%s\n"
 		   "FPU:\t\tnone\n"
 		   "Clocking:\t%u.%02u MHz\n"
 		   "BogoMips:\t%lu.%02lu\n"
 		   "Calibration:\t%lu loops\n",
 		   cpuinfo.cpu_impl,
+		   CONFIG_NIOS2_ARCH_REVISION,
 		   cpuinfo.mmu ? "present" : "none",
 		   clockfreq / 1000000, (clockfreq / 100000) % 10,
 		   (loops_per_jiffy * HZ) / 500000,

arch/nios2/platform/Kconfig.platform

@@ -52,6 +52,14 @@ config NIOS2_DTB_SOURCE
 
 comment "Nios II instructions"
 
+config NIOS2_ARCH_REVISION
+	int "Select Nios II architecture revision"
+	range 1 2
+	default 1
+	help
+	  Select between Nios II R1 and Nios II R2 . The architectures
+	  are binary incompatible. Default is R1 .
+
 config NIOS2_HW_MUL_SUPPORT
 	bool "Enable MUL instruction"
 	default n