drm/ast: Load lut in crtc_commit

In the past the ast driver relied upon the fbdev emulation helpers to
call ->load_lut at boot-up. But since

commit b8e2b019
Author: Peter Rosin <peda@axentia.se>
Date:   Tue Jul 4 12:36:57 2017 +0200

    drm/fb-helper: factor out pseudo-palette

that's cleaned up and drivers are expected to boot into a consistent
lut state. This patch fixes that.

Fixes: b8e2b019 ("drm/fb-helper: factor out pseudo-palette")
Cc: Peter Rosin <peda@axenita.se>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: <stable@vger.kernel.org> # v4.14+
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=198123
Cc: Bill Fraser <bill.fraser@gmail.com>
Reported-and-Tested-by: NBill Fraser <bill.fraser@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/ast/ast_mode.c

@@ -644,6 +644,7 @@ static void ast_crtc_commit(struct drm_crtc *crtc)
 {
 	struct ast_private *ast = crtc->dev->dev_private;
 	ast_set_index_reg_mask(ast, AST_IO_SEQ_PORT, 0x1, 0xdf, 0);
+	ast_crtc_load_lut(crtc);
 }