For some pixel formats .cpp structure in drm_format info it's not
enough to describe the peculiarities of the pixel layout, for example
tiled formats or packed formats at bit level.

What's implemented here is to add three new members to drm_format_info
that could describe such formats:

- char_per_block[3]
- block_w[3]
- block_h[3]

char_per_block will be put in a union alongside cpp, for transparent
compatibility  with the existing format descriptions.

Regarding, block_w and block_h they are intended to be used through
their equivalent getters drm_format_info_block_width /
drm_format_info_block_height, the reason of the getters is to abstract
the fact that for normal formats block_w and block_h will be unset/0,
but the methods will be returning 1.

Additionally, convenience function drm_format_info_min_pitch had been
added that computes the minimum required pitch for a given pixel
format and buffer width.

Using that the following drm core functions had been updated to
generically handle both block and non-block formats:

- drm_fb_cma_get_gem_addr: for block formats it will just return the
  beginning of the block.
- framebuffer_check: Use the newly added drm_format_info_min_pitch.
- drm_gem_fb_create_with_funcs: Use the newly added
  drm_format_info_min_pitch.
- In places where is not expecting to handle block formats, like fbdev
  helpers I just added some warnings in case the block width/height
  are greater than 1.

Changes since v3:
 - Add helper function for computing the minimum required pitch.
 - Improve/cleanup documentation

Changes since v8:
 - Fixed build on 32bits arm architectures, with:

-       return DIV_ROUND_UP((u64)buffer_width * info->char_per_block[plane],
+       return DIV_ROUND_UP_ULL((u64)buffer_width * info->char_per_block[plane],

Reviewed-by: Brian Starkey <brian.starkey@arm.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181101170055.5433-1-alexandru-cosmin.gheorghe@arm.com