Edge: fixup NULL pointer dereference when change the resolution

[   57.068051] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[   57.068806] pgd = ffffffc0ea34f000
[   57.069113] [00000000] *pgd=0000000000000000, *pud=0000000000000000
[   57.069757] Internal error: Oops: 96000005 [#1] SMP
[   57.070194] Modules linked in: zram lz4_compress lzo_compress
[   57.070745] CPU: 1 PID: 753 Comm: Xorg Not tainted 4.4.143 #5
[   57.071250] Hardware name: Khadas Edge (DT)
[   57.071628] task: ffffffc0e5d23600 task.stack: ffffffc0e5d9c000
[   57.072156] PC is at vop_crtc_bandwidth+0x240/0x30c
[   57.072591] LR is at vop_crtc_bandwidth+0x12c/0x30c
[   57.073026] pc : [<ffffff80084c39d8>] lr : [<ffffff80084c38c4>] pstate: 60000145
[   57.073669] sp : ffffffc0e5d9faf0
[   57.073964] x29: ffffffc0e5d9faf0 x28: 0000000000000010
[   57.074448] x27: ffffffc0d5fae200 x26: 0000000000000001
[   57.074930] x25: 0000000000000002 x24: ffffffc0e5f35a00

Author: numbqq

drivers/gpu/drm/rockchip/rockchip_drm_vop.c

@@ -63,7 +63,7 @@
 		VOP_REG_SUPPORT(vop, win->phy->name)
 
 #define VOP_WIN_SCL_EXT_SUPPORT(vop, win, name) \
-		(win->phy->scl->ext && \
+		(win && win->phy && win->phy->scl && win->phy->scl->ext && \
 		VOP_REG_SUPPORT(vop, win->phy->scl->ext->name))
 
 #define VOP_CTRL_SUPPORT(vop, name) \