drm: omapdrm: reduce clang stack usage

The thread sanitizer makes the stack usage explode from extra variable
spills in dispc_runtime_resume:

drivers/gpu/drm/omapdrm/dss/dispc.c:4735:27: error: stack frame size (1824) exceeds limit (1280) in 'dispc_runtime_resume' [-Werror,-Wframe-larger-than]

I could not figure out what exactly is going on here, but I see that
whenever dispc_restore_context() is not inlined, that function
and its caller shrink below 900 bytes combined of stack usage.

Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Tomi Valkeinen <[e-mail]>

drivers/gpu/drm/omapdrm/dss/dispc.c

···
 	DSSDBG("context saved\n");
 }
 
-static void dispc_restore_context(struct dispc_device *dispc)
+static noinline_for_stack void dispc_restore_context(struct dispc_device *dispc)
 {
 	int i, j;