arm/dt: msm8974: remove sd card regulator's "always-on" flag

One of the SD card's regulator was marked as "always-on" but that is not
needed. Removing the "always-on" marking to increase power savings.

CRs-fixed: 424620
Change-Id: I973bf61309aba98eb906f93fea69158795cb603e
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>