ARM: cache-v7: use movw/movt instructions

We always build cache-v7.S for ARMv7, so we can use the ARMv7 16-bit
move instructions to load large constants, rather than using constants
in a literal pool.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>