drm/gma: Remove calls to kmap()

kmap() is being deprecated and these instances are easy to convert to
kmap_local_page().

Furthermore, in gma_crtc_cursor_set() use the memcpy_from_page() helper
instead of an open coded use of kmap_local_page().

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220124015409.807587-4-ira.weiny@intel.com