V4L/DVB (9244): video: improve sh_mobile_ceu buffer handling

This patch improves the buffer handling in the sh_mobile_ceu driver.

Instead of marking all queued buffers as VIDEOBUF_ACTIVE the code now
marks queued-but-not-active buffers as VIDEOBUF_QUEUED and buffers
involved in dma as VIDEOBUF_ACTIVE. The code is also updated with
code to cancel active buffers, thanks to Morimoto-san.

Tested-by: Kuninori Morimoto <morimoto.kuninori@renesas.com>
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>