ARM: tegra: build assembly files with -march=armv7-a

The tegra assembly files are written for ARMv7 and are not compatible
with ARMv6, which leads to build warnings when compiling a dual
ARMv6/v7 kernel. Since this code is only ever run on Tegra ARMv7
hardware, we can tell the assembler which architecture level to
use.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-tegra/Makefile

+asflags-y				+= -march=armv7-a
+
 obj-y                                   += common.o
 obj-y                                   += io.o
 obj-y                                   += irq.o