headers: Update drm_sarea.h

Generated using make headers_install. Only difference is a new value
of SAREA_MAX for mips. Not that we ever shipped a dri1 driver on that
platform probably ...

Generated fromd drm-misc commit 249c4f538b1aae55d41699f8bafc6cb762a7f48f

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>