media: imx: imx7-media-csi: Merge hw_reset() with init_interface()

The imx7_csi_hw_reset() and imx7_csi_init_interface() functions are
always called together. Merge them. This allows simplifying the code by
avoiding duplicated register writes.

As the imx7_csi_hw_reset() function didn't perform a hardware reset by
initialized the registers to reset defaults (in addition to resetting
the frame counter), name the resulting function imx7_csi_init_default()
as it sets default values.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>