drm/komeda: Correct d71 register block counting

Per HW, d71->num_blocks includes reserved blocks but no PERIPH block,
correct the block counting accordingly.
D71 happens to only have one reserved block and periph block, which
hides this counting error.

Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@arm.com>
Reviewed-by: Mihail Atanassov <mihail.atanassov@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210061015.25905-1-james.qian.wang@arm.com