[MIPS] Fix BUG(), BUG_ON() handling

With commit 63dc68a8cf, kernel can not
handle BUG() and BUG_ON() properly since get_user() returns false for
kernel code.  Use __get_user() to skip unnecessary access_ok().  This
patch also make BRK_BUG code encoded in the TNE instruction.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-mips/bug.h

@@ -18,7 +18,8 @@ do {									\
 
 #define BUG_ON(condition)						\
 do {									\
-	__asm__ __volatile__("tne $0, %0" : : "r" (condition));		\
+	__asm__ __volatile__("tne $0, %0, %1"				\
+			     : : "r" (condition), "i" (BRK_BUG));	\
 } while (0)
 
 #define HAVE_ARCH_BUG_ON