AMD boards (non-AGESA): Cleanup earlymtrr.c includes

Change-Id: I5f4bf9dbaf3470dc83d3e980bb6cab10801e15c1
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/4523
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>

src/include/cpu/x86/mtrr.h

@@ -92,6 +92,10 @@ static inline long x86_mtrr_rom_cache_var_index(void) { return -1; }
 
 #endif
 
+#if !defined(__ASSEMBLER__) && defined(__PRE_RAM__) && !defined(__ROMCC__)
+void set_var_mtrr(unsigned reg, unsigned base, unsigned size, unsigned type);
+#endif
+
 #if !defined(CONFIG_RAMTOP)
 # error "CONFIG_RAMTOP not defined"
 #endif