ARM: l2c: rename cache_wait_way()

cache_wait_way() is actually used to wait for a particular mask to
report clear; it's not really got much to do with cache ways at all.
Indeed, it gets used to wait for the C bit to clear on older caches.
Rename this with a more generic function name which better reflects
its purpose: l2c_wait_mask().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>