drm/i915/gvt: mark symbols static where possible

Mark all local functions & variables as static.

Signed-off-by: Du, Changbin <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/gvt/display.c b/drivers/gpu/drm/i915/gvt/display.c
index d8908d4..c0c884a 100644
--- a/drivers/gpu/drm/i915/gvt/display.c
+++ b/drivers/gpu/drm/i915/gvt/display.c
@@ -120,7 +120,7 @@
 
 #define DPCD_HEADER_SIZE        0xb
 
-u8 dpcd_fix_data[DPCD_HEADER_SIZE] = {
+static u8 dpcd_fix_data[DPCD_HEADER_SIZE] = {
 	0x11, 0x0a, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
 };