sh: Fix up binfmt_flat compile warnings.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

include/asm-sh/flat.h

@@ -19,6 +19,6 @@
 #define	flat_get_addr_from_rp(rp, relval, flags, p)	get_unaligned(rp)
 #define	flat_put_addr_at_rp(rp, val, relval)	put_unaligned(val,rp)
 #define	flat_get_relocate_addr(rel)		(rel)
-#define	flat_set_persistent(relval, p)		0
+#define	flat_set_persistent(relval, p)		({ (void)p; 0; })
 
 #endif /* __ASM_SH_FLAT_H */