clk: qcom: Add properties for marking clocks as critical

Some clocks are critical only on specific boards, i.e. clocks used to
interface with external PMICs over I2C. Which clocks are critical depend
on which I2C bus is chosen to connect the PMICs. To support this, add
properties to set QCOM_CLK_IS_CRITICAL on a per-board basis.

The qcom,critical-clocks property can be used to set
QCOM_CLK_IS_CRITICAL on individual clocks.

The qcom,critical-devices property can be used to set
QCOM_CLK_IS_CRITICAL on all clocks used by specified devices.

Change-Id: I42d61ec13225026ba7d0b78079cf7a2ab67339f2
Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>