drm: drm_fourcc: Introduce macro-pixel info to drm_format_info

drm: drm_fourcc: Introduce macro-pixel info to drm_format_info

Multiple pixels can be grouped as a single unit and form a 'macro-pixel'.
This is to model formats where multiple non-byte aligned pixels are stored
together in a byte-aligned way. For example, if 3 - 10 bit
pixels are stored in 32 bit, the 32 bit stroage can be treated as
a single macro-pixel with 3 pixels. This aligns non-byte addressable
formats with drm core where each pixel / component is expected to be
byte aligned.

Add 'pixels_per_macro' to note how many pixels are in a macro-pixel.
'bytes_per_macro' specifies the size of a macro-pixel in bytes.

Signed-off-by: Hyun Kwon <hyun.kwon@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>