p54: per-device names

This patch replaces the static "p54:" strings in front of most printk's
with their corresponding per-device names.

It was always a bit of a hassle to check which device was
generating all the messages.

Signed-off-by: Christian Lamparter <chunkeey@web.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>