mmc: msm_sdcc: Clean up card detect code based on polarity

This patch simplifies the code needed to handle both ACTIVE LOW and
ACTIVE HIGH cases for SD card detect gpio line when the card is present.

Change-Id: I6cfdf0fea4992204ef4cfbefe4dc63bfc8ae3033
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>