drm/nouveau: change base917c_format from global to static

Smatch reports this issue
base917c.c:26:1: warning: symbol 'base917c_format'
  was not declared. Should it be static?

base917c_format is only used in base917.c.  Single
file variables should not be global so change
base917c_format's storage-class specifier to static.
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/20220418141842.296386-1-trix@redhat.com

drivers/gpu/drm/nouveau/dispnv50/base917c.c

@@ -22,7 +22,7 @@
 #include "base.h"
 #include "atom.h"
 
-const u32
+static const u32
 base917c_format[] = {
 	DRM_FORMAT_C8,
 	DRM_FORMAT_XRGB8888,