Change email address for 8250_pci

I'm still receiving reports to my email address, so let's point this
at the linux-serial mailing list instead.

Cc: <stable@vger.kernel.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>