mmc: mxs: fix card detection in case of 'broken-cd' flag set

In case of reboot my olinuxino imx23 board does not see
mmc card any more. mmc_rescan is being called by delayed
work in loop, but mxs_mmc_get_cd always returns 0, so we
will never pass the card detection check and will not do
further card inition.

This patch is just an attempt to partially revert the patch
a91fe279 of Sascha Hauer, where it is claimed that upper
layer will handle broken card detection using the polling
logic and MMC_CAP_NEEDS_POLL capability, but seems it is not
true, because upper logic still expects 1 from 'get_cd'.

So, here we always return 1 (card present) in case of
MMC_CAP_NEEDS_POLL capability set.

Signed-off-by: Roman Pen <r.peniaev@gmail.com>
CC: Chris Ball <chris@printf.net>
CC: Sascha Hauer <s.hauer@pengutronix.de>
CC: Fabio Estevam <fabio.estevam@freescale.com>
CC: Shawn Guo <shawn.guo@linaro.org>
CC: Ulf Hansson <ulf.hansson@linaro.org>
CC: linux-mmc@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>