[PCMCIA] inform user of insertion and ejection events

Print out minimal information in dmesg whnever a CardBus or PCMCIA card
is inserted into or ejected from a slot. This will make debugging certain
types of bugs much easier, and is similar to output produced by other
hotpluggable buses.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>