microblaze: Remove getenv_IPaddr prototype

Commit 6a45e384955262882375a2785426dc65aeb636c4
should remove reference from Microblaze too.

Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/lib_microblaze/board.c b/lib_microblaze/board.c
index 200ea5d..d4baea9 100644
--- a/lib_microblaze/board.c
+++ b/lib_microblaze/board.c
@@ -43,7 +43,6 @@
 #endif
 #if defined(CONFIG_CMD_NET)
 extern int eth_init (bd_t * bis);
-extern int getenv_IPaddr (char *);
 #endif
 
 /*