phy: qcom-qmp-combo: Move phy_mutex out of com_init/exit

With the upcoming introduction of USB Type-C orientation switching the
region of mutual exclusion needs to be extended to cover both the common
init/exit as well as the individual functions.

So move the phy_mutex one step up the stack.

Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Abel Vesa <abel.vesa@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on HDK8450
Tested-by: Johan Hovold <johan+linaro@kernel.org>	# X13s
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Link: https://lore.kernel.org/r/20230515032743.400170-3-quic_bjorande@quicinc.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>