drm/komeda: Unify mclk/pclk/pipeline->aclk to one MCLK

Current komeda driver uses three dedicated clks for a specific purpose:
- mclk: main engine clock
- pclk: APB clock
- pipeline->aclk: AXI clock.

But per spec the komeda HW only has three input clks:
- ACLK: used for AXI masters, APB slave and most pipeline processing
- PXCLK for pipeline 0: output pixel clock for pipeline 0
- PXCLK for pipeline 1: output pixel clock for pipeline 1

So one ACLK is enough, no need to split it to three mclk/pclk/axiclk.
drop pclk/pipeline->axiclk. but only keep one mclk in komeda driver.

Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>