media: videobuf2: add queue memory coherency parameter

Preparations for future V4L2_MEMORY_FLAG_NON_COHERENT support.

Extend the vb2_core_reqbufs() parameters list to accept requests'
->flags, which will be used for memory coherency configuration.

An attempt to allocate a buffer with coherency requirements
that do not match the queue's consistency model will fail.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>