video: Skip framebuffer reservation if already reserved

video: Skip framebuffer reservation if already reserved

Skip framebufer reservation if it was already reserved from previous
stage and whose information was passed using a bloblist.

Return error in case framebuffer information received from bloblist is
invalid i.e NULL or empty.

While at it, improve the debug message to make it more clear that
address in discussion is of framebuffer and not bloblist and also match
it with printing scheme followed in video_reserve function.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>