mark set but unused variables as such

SVN-Revision: 31296

target/linux/rb532/patches-2.6.32/003-unused_variables.patch

@@ -0,0 +1,11 @@
+--- a/arch/mips/rb532/prom.c
++++ b/arch/mips/rb532/prom.c
+@@ -73,7 +73,7 @@ void __init prom_setup_cmdline(void)
+ 	static char cmd_line[CL_SIZE] __initdata;
+ 	char *cp, *board;
+ 	int prom_argc;
+-	char **prom_argv, **prom_envp;
++	char **prom_argv, **prom_envp __maybe_unused;
+ 	int i;
+ 
+ 	prom_argc = fw_arg0;