trivial: Add a space (and a comma) to a printk in 8250 driver

Commit d87a6d95

 ("drivers/serial/: remove CVS keywords") removed one
space too many in the printk in serial8250_init(). Put it back in (and
add a comma for clarity).

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>