[MIPS] Workaround for a sparse warning in include/asm-mips/compat.h

Cast to a __user pointer via "unsigned long" to get rid of this warning:

include2/asm/compat.h:135:10: warning: cast adds address space to expression (<asn:1>)
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/compat.h

@@ -132,7 +132,8 @@ typedef u32		compat_uptr_t;
 
 static inline void __user *compat_ptr(compat_uptr_t uptr)
 {
-	return (void __user *)(long)uptr;
+	/* cast to a __user pointer via "unsigned long" makes sparse happy */
+	return (void __user *)(unsigned long)(long)uptr;
 }
 
 static inline compat_uptr_t ptr_to_compat(void __user *uptr)