media: am437x-vpfe: TRY_FMT ioctl is not really trying anything

The try_fmt was not actually trying out the provided format
but merely returning the current format basically like get_fmt.
In addition set_fmt should first invoked try_fmt to validate the
given format before applying it to the hardware.

To fix all of these the whole get/try/set ioctl functions had to
be reworked.
When calculating the bytesperline/stride and sizeimage format
member we don't need to locally store the current value of
bytesperpixel as it can easily get derived dynamically.
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Acked-by: Lad Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/am437x/am437x-vpfe.h

@@ -281,8 +281,8 @@ struct vpfe_device {
 	struct vpfe_cap_buffer *next_frm;
 	/* Used to store pixel format */
 	struct v4l2_format fmt;
-	/* Used to store current bytes per pixel based on current format */
-	unsigned int bpp;
+	/* Used to keep a reference to the current vpfe_fmt */
+	struct vpfe_fmt *current_vpfe_fmt;
 	struct vpfe_fmt	*active_fmt[VPFE_NUM_FORMATS];
 	unsigned int num_active_fmt;