zynqmp: pm: Reimplement clock enable EEMI API

zynqmp: pm: Reimplement clock enable EEMI API

Clock enable EEMI API is reimplemented to use system-level clock
and pll EEMI APIs rather than direct MMIO read/write accesses to clock
and pll control registers.
Since linux still uses clock enable API to trigger locking of the PLLs
in the pm_clock_enable() implementation we need to workaround this by
distinguishing two cases: 1) if the given clock ID corresponds to a PLL
output clock ID; or 2) given clock ID is truly an on-chip clock that can
be gated.
For case 1) we'll call pm_api_clock_pll_enable() implemented in
pm_api_clock.h/c. This function checks what is the buffered PLL mode and
calls the system-level PLL set mode EEMI API with the buffered mode value
specified as argument. Long term, if linux driver get fixed to use PLL
EEMI API to control PLLs, this case could be removed from ATF.
For case 2) we'll call the PMU to configure the clock gate. This is done
using system-level clock enable EEMI API.

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Acked-by: Will Wong <WILLW@xilinx.com>
Signed-off-by: Jolly Shah <jollys@xilinx.com>