msm: clock-8x60: Move smi_2x clk_enable to prepare phase

The smi_2x clock branch needs to be enabled before enabling the
RPM's smi clock. This requirement is currently enforced by making
the smi_2x clock a 'depends' clock for the smi clock. We want to
move the RPM clock control code to prepare/unprepare but that
will break this dependency because the smi_2x clock is enabled in
the enable step, not the prepare step.

Move the enable/disable ops for the smi_2x clock to the
prepare/unprepare phase so that it is enabled before we send a
command to enable the RPM smi clock.

Change-Id: If9e2b8ead7f3202eedd75023f2cf960c7aa59714
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>