libpayload: add march flag for armv7

The cache functions for armv7 require 'march=armv7-a' to use
the 'isb' and 'dsb' instructions.

Change-Id: I3b7ad8fc7da8c3167b38fd1a325090fe49e4ca42
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6668
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
1 file changed