arm64: dts: qcom: sdm845-mtp: Mark protected gcc clocks

As of v4.20-rc1 probing the GCC driver on a SDM845 device with the
standard security implementation causes an access violation and an
immediate system restart. Use the protected-clocks property to mark the
offending clocks protected for the MTP, in order to allow it to boot.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>