drm_hwcomposer: stop using pixel_stride

drm_hwcomposer: stop using pixel_stride

pixel_stride is used only to validate buffer when importing using
GraphicBufferMapper::importBuffer() method.

The problem is we can't always get this value from buffer_handle_t.
Libdrm and MapperMetadata getters can only calculate this value based
on byte stride and buffer format. But this calculation isn't always
possible, which causes importBuffer() to fail.

Instead we can use GrallocMapper::importBuffer() method,
which doesn't require to validate the buffer.

This commit is not compatible with Android-P.

Signed-off-by: Roman Stratiienko <r.stratiienko@gmail.com>