arm/dt: msm8226: Use active only regulator for sr2_pll

Since power collapse is atomic, prepare/unprepare ops cannot be used to
remove a vote on a normal regulator. Therefore, use an active-only
regulator to ensure the vote is removed during the sleep set. Fix this
issue for both 8226 and 8610.

Change-Id: I380986a7631ad86adc796d8c484e02a0d95d4c34
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>