egl: add width/height as EXT_image_dma_buf_import attrs

egl: add width/height as EXT_image_dma_buf_import attrs

Although not listed amongst the initial EGL_LINUX_DRM_FOURCC_EXT and
friends list, the spec reads

   ... Required attributes and their values are as
   follows:

    * EGL_WIDTH & EGL_HEIGHT: The logical dimensions of the buffer in pixels

    * EGL_LINUX_DRM_FOURCC_EXT: The pixel format of the buffer, as specified
      by drm_fourcc.h and used as the pixel_format parameter of the
      drm_mode_fb_cmd2 ioctl.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>