arm: dts: msm8610: fix SDC2 regulator to be turned-off

The LDO21 powering the SDC2 slot has been marked as
always-on. But this can be turned-off during
runtime/system suspend.

This patch removes the always-on attribute of this
regulator.

CRs-fixed: 511572
Change-Id: I9744a581ed2deb967da3f9cb4080de75160de236
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>