microblaze: Remove getenv_IPaddr prototype

Commit 6a45e384
should remove reference from Microblaze too.
Signed-off-by: NMichal Simek <monstr@monstr.eu>

lib_microblaze/board.c

@@ -43,7 +43,6 @@ extern int interrupts_init (void);
 #endif
 #if defined(CONFIG_CMD_NET)
 extern int eth_init (bd_t * bis);
-extern int getenv_IPaddr (char *);
 #endif
 
 /*