bug: when !CONFIG_BUG, make WARN call no_printk to check format and args

The stub version of WARN for !CONFIG_BUG completely ignored its format
string and subsequent arguments; make it check them instead, using
no_printk.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>