drm_hwcomposer: platformhisi: Add support for importing DRM_FORMAT_YVU420 buffers

When trying to play fullscreen video, I started seeing import
errors, which were caused by us trying to call drmModeAddFB2()
with fmt DRM_FORMAT_YVU420 but only setting the a single set of
handle/pitch/offset values.

In the kernel, the framebuffer_check() function would then fail
with "no buffer object handle for plane 1" since we only passed
one plane in.

Thus this patch calculates and sets the pitch/offset values for
the separate planes in the single gem_handle buffer.

Many thanks to Stefan Schake and Rob Herring for helping me
understand some of the subtleties of image plans vs display
planes, etc.

Change-Id: I2d9bdfc66c504e6446a4f9c6287ab675201afa30
Signed-off-by: John Stultz <john.stultz@linaro.org>
1 job for fix-yuv-handling in 41 seconds (queued for 16 seconds)