sdl12-compat: Fix typo

SDL Commits
1 
From d02e6f36df87b8fbb129082380671213ebd53f41 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 31 May 2021 00:09:17 -0400
Subject: [PATCH] Fix typo

---
 src/SDL12_compat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/SDL12_compat.c b/src/SDL12_compat.c
index b00e25b..157c592 100644
--- a/src/SDL12_compat.c
+++ b/src/SDL12_compat.c
@@ -2787,7 +2787,7 @@ SetPalette12ForMasks(SDL12_Surface *surface12, const Uint32 Rmask, const Uint32
         LOSSMASKSHIFTSETUP(R);
         LOSSMASKSHIFTSETUP(G);
         LOSSMASKSHIFTSETUP(B);
-        #undef LOSSMASSSHIFTSETUP
+        #undef LOSSMASKSHIFTSETUP
         format12->Amask = 0;
         format12->Ashift = 0;
         format12->Aloss = 8;