Building a multiplatform kernel with combined armv7 and armv6
kernel does not work with the socfpga smp code, which contains
v7-only instructions. Since this code never runs on armv6,
we can annotate the assmebly with .arch   armv7-a, as suggested
by Russell King.

[arnd: reword commit message]
Signed-off-by: NPavel Machek <pavel@denx.de>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>