drm/rockchip: vop2: fix uninitialized variable possible_crtcs

clang reportes this error
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2322:8: error:
  variable 'possible_crtcs' is used uninitialized whenever 'if'
  condition is false [-Werror,-Wsometimes-uninitialized]
                        if (vp) {
                            ^~
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2336:36: note:
  uninitialized use occurs here
                ret = vop2_plane_init(vop2, win, possible_crtcs);
                                                 ^~~~~~~~~~~~~~
drivers/gpu/drm/rockchip/rockchip_drm_vop2.c:2322:4:
  note: remove the 'if' if its condition is always true
                        if (vp) {
                        ^~~~~~~~

The else-statement changes the win->type to OVERLAY without setting the
possible_crtcs variable.  Rework the block, initialize possible_crtcs to
0 to remove the else-statement.  Split the else-if-statement out to its
own if-statement so the OVERLAY check will catch when the win-type has
been changed.

Fixes: 368419a2 ("drm/rockchip: vop2: initialize possible_crtcs properly")
Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316132302.531724-1-trix@redhat.com

drivers/gpu/drm/rockchip/rockchip_drm_vop2.c

@@ -2301,7 +2301,7 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 	nvp = 0;
 	for (i = 0; i < vop2->registered_num_wins; i++) {
 		struct vop2_win *win = &vop2->win[i];
-		u32 possible_crtcs;
+		u32 possible_crtcs = 0;
 
 		if (vop2->data->soc_id == 3566) {
 			/*
@@ -2327,12 +2327,11 @@ static int vop2_create_crtcs(struct vop2 *vop2)
 				/* change the unused primary window to overlay window */
 				win->type = DRM_PLANE_TYPE_OVERLAY;
 			}
-		} else if (win->type == DRM_PLANE_TYPE_OVERLAY) {
-			possible_crtcs = (1 << nvps) - 1;
-		} else {
-			possible_crtcs = 0;
 		}
 
+		if (win->type == DRM_PLANE_TYPE_OVERLAY)
+			possible_crtcs = (1 << nvps) - 1;
+
 		ret = vop2_plane_init(vop2, win, possible_crtcs);
 		if (ret) {
 			drm_err(vop2->drm, "failed to init plane %s: %d\n",