drm/nouveau/disp/gv100: make gv100_disp_wndw and gv100_disp_wndw_mthd static

Sparse reports these issues
wndwgv100.c:120:1: warning: symbol 'gv100_disp_wndw_mthd' was not declared. Should it be static?
wndwgv100.c:140:1: warning: symbol 'gv100_disp_wndw' was not declared. Should it be static?

These variable are only used in wndwgv100.c.  Single file variables should be static.
So use static as their storage-class specifiers.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220425131308.158635-1-trix@redhat.com

drivers/gpu/drm/nouveau/nvkm/engine/disp/wndwgv100.c

@@ -116,7 +116,7 @@ gv100_disp_wndw_mthd_base = {
 	}
 };
 
-const struct nv50_disp_chan_mthd
+static const struct nv50_disp_chan_mthd
 gv100_disp_wndw_mthd = {
 	.name = "Window",
 	.addr = 0x001000,
@@ -136,7 +136,7 @@ gv100_disp_wndw_intr(struct nv50_disp_chan *chan, bool en)
 	nvkm_mask(device, 0x611da4, mask, data);
 }
 
-const struct nv50_disp_chan_func
+static const struct nv50_disp_chan_func
 gv100_disp_wndw = {
 	.init = gv100_disp_dmac_init,
 	.fini = gv100_disp_dmac_fini,