include: uapi: v4l2: Add additional pixel formats for use with PiSP

Add the following formats:

- V4L2_PIX_FMT_RGB48/V4L2_PIX_FMT_BGR48
  48-bit RGB where each colour sample is 16-bits.

- V4L2_PIX_FMT_PISP_COMP1_MONO/V4L2_PIX_FMT_PISP_COMP2_MONO
  16-bit to 8-bit pisp compressed monochrome pixel format.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>