ARM: l2c: remove outer_inv_all() method

No one ever calls this function anywhere in the kernel, so let's
completely remove it from the outer cache API and turn it into an
internal-only thing.

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

diff --cc arch/arm/include/asm/outercache.h
Simple merge

diff --cc arch/arm/mm/cache-feroceon-l2.c
Simple merge

diff --cc arch/arm/mm/cache-l2x0.c
Simple merge