media: venus: firmware: check fw size against DT memory region size

By historical reasons we defined firmware memory size to be 6MB even
that the firmware size for all supported Venus versions is 5MBs. Correct
that by compare the required firmware size returned from mdt loader and
the one provided by DT reserved memory region. We proceed further if the
required firmware size is smaller than provided by DT memory region.

Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>