clk: qcom: Support 'protected-clocks' property

Certain firmware configurations "protect" clks and cause the entire
system to reboot when a non-secure OS such as Linux tries to read or
write protected clk registers. But other firmware configurations allow
reading or writing the same registers, and they may actually require
that the OS use the otherwise locked down clks. Support the
'protected-clocks' property by never registering these protected clks
with the common clk framework. This way, when firmware is protecting
these clks we won't have the chance to ever read or write these
registers and take down the entire system.

Cc: Taniya Das <tdas@codeaurora.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>