pcmcia: avoid validate_cis failure on CIS override

Commit a8408c17 introduced a new check to pccard_validate_cis(),
which avoids any "late" calls to this function. This broke the
insertion of cards which require a CIS override which changes
the number of card functions. Fix this by asserting that this
is _not_ a late call, but a proper call early during the card
insertion process.

Fixes https://bugzilla.kernel.org/show_bug.cgi?id=16138

Reported-by: Mikulas Patocka <mpatocka@redhat.com>
CC: <stable@kernel.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>