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.

CRs-Fixed: 490017
Change-Id: Ica764565745ea0b54300e38157c58c0aa643291d
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>