[media] Revert "[media] v4l2: vb2: one more fix for REQBUFS()"

This reverts commit 31901a07.

Queue should be reinitialized on each REQBUFS() call even if the memory
access method and buffer count have not been changed. The user might have
changed the format and if we go the short path introduced in that commit,
the memory buffer will not be reallocated to fit with new format.

The previous patch was just over-engineered optimization, which just
introduced a bug to videobuf2.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
CC: Pawel Osciak <pawel@osciak.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>