serial: 8250_pci: clean up printk() calls

Move the printk() calls to to dev_*() instead, to tie into the dynamic
debugging infrastructure.

Also change some "raw" printk() calls to dev_err() to provide a better
error message to userspace so it can properly identify the device and
not just have to guess.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>