Blackfin: Convert BUG() to use unreachable()

Use the new unreachable() macro instead of for(;;);
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/bug.h

@@ -47,7 +47,7 @@
 #define BUG()								\
 	do {								\
 		_BUG_OR_WARN(0);					\
-		for (;;);						\
+		unreachable();						\
 	} while (0)
 
 #define WARN_ON(condition)							\