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