clk: qcom: gcc-sdm845: Add support to control the GCC_GPU_IREF_EN signal

The gcc_gpu_iref_clk will be controlled by the GPU driver.
Add the programming support for it and provide the clock
handle to be used.

Change-Id: I0f4270083c6c43cb2938070cec83f3be35921261
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>