efi_loader: static functions in efi_console.c

Define function set_shift_mask() as static as it is not used externally.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_console.c b/lib/efi_loader/efi_console.c
index 1ed8c7a..4317630 100644
--- a/lib/efi_loader/efi_console.c
+++ b/lib/efi_loader/efi_console.c
@@ -669,7 +669,7 @@
  * @mod:	Xterm shift mask
  * @key_state:  receives the state of the shift, alt, control, and logo keys
  */
-void set_shift_mask(int mod, struct efi_key_state *key_state)
+static void set_shift_mask(int mod, struct efi_key_state *key_state)
 {
 	key_state->key_shift_state = EFI_SHIFT_STATE_VALID;
 	if (mod) {