dev: Add dev_vprintk_emit and dev_printk_emit

Add utility functions to consolidate the use of
create_syslog_header and vprintk_emit.

This allows conversion of logging functions that
call create_syslog_header and then call vprintk_emit
or printk_emit to the dev_ equivalents.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>