clk: qcom: clk-rpmh: Wait for completion when enabling clocks

The current implementation always uses rpmh_write_async, which doesn't
wait for completion. That's fine for disable requests since there's no
immediate need for the clocks and they can be disabled in the
background. However, for enable requests we need to ensure the clocks
are actually enabled before returning to the client. Otherwise, clients
can end up accessing their HW before the necessary clocks are enabled,
which can lead to bus errors.

Use the synchronous version of this API (rpmh_write) for enable requests
in the active set to ensure completion.

Completion isn't required for sleep/wake sets, since they don't take
effect until after we enter sleep. All rpmh requests are automatically
flushed prior to entering sleep.

Change-Id: I3d3261159bb30e4e149f4cb6b3e9d60b018a5d5e
Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>