[SCSI] make pcmcia directory use obj-y|m instead of subdir-y|m

subdir-y|m isn't supposed to contain modules or built-in components.
Change subdir-$(CONFIG_PCMCIA) to obj-$(CONFIG_PCMCIA).

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>