Clock set parent 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 set parent API to set pre_src, post_src, div2
and bypass, in the implementation of pm_clock_set_parent() we need to
workaround this by distinguishing two cases:
1) if the given clock ID corresponds to a PLL-related clock ID (*_PRE_SRC,
*_POST_SRC, *_INT_MUX or *PLL clock IDs); or 2) given clock ID is truly
an on-chip clock.
For case 1) we'll map the call onto PLL set parameter EEMI API with the
respective parameter ID. Since clock set parent interface to EL1/2 receives
parent index (mux select value), the value is just passed to PMU.
Functions that appear to be unused after this change is made are removed.

Setting the parent of *PLL clocks, that actually model bypass, is not
possible. This is already ensured by the existing clock model having the
CLK_SET_RATE_NO_REPARENT flag. The API also doesn't allow changing the
bypass parent. Bypass is controlled only by the PMU firmware.

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