pcmcia net: use roundup_pow_of_two() macro instead of grotesque loop

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>