Remove extern keyword from function declarations

Function declarations implicitly have external linkage so do not
need the extern keyword.

Change-Id: Ia0549786796d8bf5956487e8996450a0b3d79f32
diff --git a/include/lib/aarch64/xlat_tables.h b/include/lib/aarch64/xlat_tables.h
index d7e1c60..a500f03 100644
--- a/include/lib/aarch64/xlat_tables.h
+++ b/include/lib/aarch64/xlat_tables.h
@@ -60,11 +60,11 @@
 	mmap_attr_t	attr;
 } mmap_region_t;
 
-extern void mmap_add_region(unsigned long base, unsigned long size,
-				unsigned attr);
-extern void mmap_add(const mmap_region_t *mm);
+void mmap_add_region(unsigned long base, unsigned long size,
+			unsigned attr);
+void mmap_add(const mmap_region_t *mm);
 
-extern void init_xlat_tables(void);
+void init_xlat_tables(void);
 
 extern uint64_t l1_xlation_table[];