Fix typo with __MIPSEB__ preprocessor check (bug #4836.)

Patch from Simon Howard

include/SDL_endian.h

@@ -45,7 +45,7 @@
 #else /* __linux__ */
 #if defined(__hppa__) || \
     defined(__m68k__) || defined(mc68000) || defined(_M_M68K) || \
-    (defined(__MIPS__) && defined(__MISPEB__)) || \
+    (defined(__MIPS__) && defined(__MIPSEB__)) || \
     defined(__ppc__) || defined(__POWERPC__) || defined(_M_PPC) || \
     defined(__sparc__)
 #define SDL_BYTEORDER   SDL_BIG_ENDIAN