Patch from Catalin Marinas

The CPU Id register changed with the ARM1176 processor and the
ARMv6 architecture description field can be either 7 or 0xF.
This patch also detects the first byte of the part number since
0xF in the description field will also be used for future ARM
architectures.

Signed-off-by: Catalin Marinas
Signed-off-by: Russell King