powerpc/fsl-booke: Fixup calc_cam_sz to support MMU v2

The registers that describe size supported by TLB are different on MMU
v2 as well as we support power of two page sizes.  For now we continue
to assume that FSL variable size array supports all page sizes up to the
maximum one reported in TLB1PS.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>