s3cmci: add better support for no card detect or write protect available

Add better support for omitting either the card detect or the write
protect GPIOs if the board does not support it.  Add the fields
no_wprotect and no_detect to the platform data which when set indicate the
absence of the respective GPIOs.

Note, this also fixes a minor bug where it tries to free IRQ0 if there is
no detect gpio available.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>