omap: Fix sev instruction usage for multi-omap

Otherwise we get the following error with omap3_defconfig and CONFIG_SMP:

Error: selected processor does not support `sev'

Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
diff --git a/arch/arm/mach-omap2/Makefile b/arch/arm/mach-omap2/Makefile
index 63b2d88..88d3a1e 100644
--- a/arch/arm/mach-omap2/Makefile
+++ b/arch/arm/mach-omap2/Makefile
@@ -25,6 +25,7 @@
 obj-$(CONFIG_HOTPLUG_CPU)		+= omap-hotplug.o
 obj-$(CONFIG_ARCH_OMAP4)		+= omap44xx-smc.o omap4-common.o
 
+AFLAGS_omap-headsmp.o			:=-Wa,-march=armv7-a
 AFLAGS_omap44xx-smc.o			:=-Wa,-march=armv7-a
 
 # Functions loaded to SRAM