[ARM] 2954/1: Allow D and I cache and branch prediction disabling for ARMv6

Patch from Catalin Marinas

There is no reason to not allow these config options. They are useful when
the hardware has problems.

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