clk: agilex: Handle clock configuration differently in SPL and U-Boot proper

clk: agilex: Handle clock configuration differently in SPL and U-Boot proper

Since warm reset may optionally set the CLock Manager to'boot mode',
the clock driver should always force the Agilex's Clock Manager to
'boot mode' before the clock driver start configuring the Clock Manager
in SPL.
In SSBL, clock driver will skip the Clock Manager configuration
if it's already being setup by SPL (Clock Manager NOT in 'boot
mode') to prevent any inaccurate clocking issues happened on HPS
peripherals such as UART, MAC and etc.

Signed-off-by: Chee Hong Ang <[email protected]>