8250_pci: Fix missing const from merges

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Antony Pavlov <antony@niisi.msk.ru>
Signed-off-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Vasily Averin <vvs@sw.ru>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>