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/bl1/bl1_private.h b/bl1/bl1_private.h
index b2ebf21..b54bf6b 100644
--- a/bl1/bl1_private.h
+++ b/bl1/bl1_private.h
@@ -34,7 +34,7 @@
 /******************************************
  * Function prototypes
  *****************************************/
-extern void bl1_arch_setup(void);
-extern void bl1_arch_next_el_setup(void);
+void bl1_arch_setup(void);
+void bl1_arch_next_el_setup(void);
 
 #endif /* __BL1_PRIVATE_H__ */