coresight: enable SD only mode when hardware sensing is not enabled

cd_gpio is floating on some devices, then there is a possiblity
that a false CARD_DETECT toggle is created when software starts to
resume SD card from power collapse at the same time. SD driver resume
will fail due to collision.

Change-Id: I5b33da09fe8d71ea2fa381f98f1dd79286d28399
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>