[ARM] 3548/1: Fix the ARMv6 CPU id in compressed/head.S

Patch from Catalin Marinas

This code was still using the old format for the ARMv6 CPU id and it wasn't
flushing the caches on the MPCore CPU (and other ARM1176 cores). The patch
changes the mask bits to cope with the new id format.

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