pcmcia: remove mailing list, update MAINTAINERS

In recent years, the linux-pcmcia mailing list gained a pretty bad
signal-to-noise ratio. It does not seem worth the hassle to keep it
any longer. Thanks to David for hosting the list for the last couple
of years!

Acked-by: David Woodhouse <dwmw2@infradead.org>
CC: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>