msm: acpuclock-krait: Disable secondary clock source gating during switches

To workaround a Krait errata on 8064, disable secondary clock source
gating during the MUX switch. This errata was already worked around
in msm-krait-l2-accessors.c in a different way, but that will soon
be removed in favor of this and some power-collapse changes.

Change-Id: I2a732e020a045384c3a4a2401ce7c819cd8de26b
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>