mmc: msm_sdcc: fix pwrsave bit handling

SDCC controller provides the PWRSAVE control bit to automatically
disable the clock to card when there is no activity with card.
SDCC driver provides the compile time option to disable this pwrsave
feature completely but some of the recent driver changes ignore this
and may enable the pwrsave feature even when its not required. This
change ensures that we always check if the pwrsave is allowed or not
before really enabling it.

Change-Id: I7a416f8ca6431613ef62402cdbf006b9f522dfdd
CRs-Fixed: 490017
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>