pcmcia: remove remaining unused IRQ_FIRST_SHARED parameter

Komuro pointed out correctly that I missed one IRQ_FIRST_SHARED
parameter in smc91c92_cs.c, and that another line could be writter
more beautifully.

CC: netdev@vger.kernel.org
CC: Komuro <komurojun-mbn@nifty.com>
Tested-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>