media: mediatek: vcodec: Drop unnecessary variable

In mtk_vcodec_mem_alloc() and mtk_vcodec_mem_free(), the value of
mem->size is not expected to change before and when using the DMA APIs
and debug print, so there's no point in keeping local copies of it.

Drop the local variable "size" in the mentioned functions, and update
printk format identifiers accordingly.

This makes the code slightly more visually consistent, and retrieve a
small amount of memory that is used for no real purpose.

Signed-off-by: Fei Shao <fshao@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>