v4l: ti-vpe: Allow usage of smaller images

The minimum width and height for VPE input/output was kept as 128 pixels. VPE
doesn't have a constraint on the image height, it requires the image width to
be atleast 16 bytes.

Change the minimum supported dimensions to 32x32. This allows us to de-interlace
qcif content. A smaller image size than 32x32 didn't make much sense, so stopped
at this.

Signed-off-by: Archit Taneja <archit@ti.com>
v4l: ti-vpe: Fix some params in VPE data descriptors

Some parameters of the VPE descriptors were understood incorrectly. They are now
fixed. The fixes are explained as follows:

- When adding an inbound data descriptor to the VPDMA descriptor list, we intend
  to use c_rect as the cropped region fetched by VPDMA. Therefore, c_rect->width
  shouldn't be used to calculate the line stride, the original image width
  should be used for that. We add a 'width' argument which gives the buffer
  width in memory.

- frame_width and frame_height describe the complete width and height of the
  client to which the channel is connected. If there are multiple channels
  fetching data and providing to the same client, the above 2 arguments should
  be the width and height of the region covered by all the channels. In the case
  where there is only one channel providing pixel data to the client
  (like in VPE), frame_width and frame_height should be the cropped width and
  cropped height respectively. The calculation of these params is done in the
  vpe driver now.

- start_h and start_v is also used in the case of multiple channels to describe
  where each channel should start filling pixel data. We don't use this in VPE,
  and pass 0s to the vpdma_add_in_dtd() helper.

- Some minor changes are made to the vpdma_add_out_dtd() helper. The c_rect
  param is removed since cropping isn't possible for outbound data, and 'width'
  is added to calculate the line stride.

Signed-off-by: Archit Taneja <archit@ti.com>
v4l: ti-vpe: Add crop support in VPE driver

Add crop ioctl ops. For VPE, cropping only makes sense with the input to VPE, or
the V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE buffer type.

For the CAPTURE type, a S_CROP ioctl results in setting the crop region as the
whole image itself, hence making crop dimensions same as the pix dimensions.

Setting the crop successfully should result in re-configuration of those
registers which are affected when either source or destination dimensions
change, set_srcdst_params() is called for this purpose.

Some standard crop parameter checks are done in __vpe_try_crop().

Signed-off-by: Archit Taneja <archit@ti.com>