device: Change dev_<level> logging functions to return void

No caller or macro uses the return value so make all
the functions return void.

Compiled x86 allyesconfig and defconfig w/o CONFIG_PRINTK

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>