device.h: Add missing inline to #ifndef CONFIG_PRINTK dev_vprintk_emit

Also add __printf() verification for format string.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>