powerpc/fsl-booke: read buffer overflow

cam[tlbcam_index] is checked before tlbcam_index < ARRAY_SIZE(cam)

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>