msm: acpuclock-8960ab: Set power collapse rate

This line was somehow left out when initially copying the
acpuclock-8960 file over to the acpuclock-8960ab file.

Without this line, power collapse leaves the Krait PLL enabled,
causing failures upon resume.

Change-Id: I1339192d59d8b7f4135b32dcb5807bfc4dababfc
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>