PCI: allow multiple calls to pcim_pin_device()

Sanity check in pcim_pin_device() was too restrictive in that it didn't
allow multiple calls to the function, which is against the devres
philosohpy of fire-and-forget.  Track pinned status separately and allow
pinning multiple times.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>