When operating in 1-bit mode, SDAT1 is used as dedicated interrupt line.
However, the 8686 will only drive this line when the ECSI bit is set in
the CCCR_IF register.

Thanks to Alagu Sankar for pointing me in the right direction.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Alagu Sankar <alagusankar@embwise.com>
Cc: Volker Ernst <volker.ernst@txtr.com>
Cc: Dan Williams <dcbw@redhat.com>
Cc: John W. Linville <linville@tuxdriver.com>
Cc: Holger Schurig <hs4233@mail.mn-solutions.de>
Cc: Bing Zhao <bzhao@marvell.com>
Cc: libertas-dev@lists.infradead.org
Cc: linux-wireless@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>