remoteproc: q6v5: Move proxy unvote to handover irq handler

Introduce interrupt handler for smp2p ready interrupt to
handle start completion. Move the proxy votes for clocks
and regulators to the handover interrupt context.

Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
[bjorn: Only proxy unvote if handover irq has not fired]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>