riscv: dts: microchip: reparent mpfs clocks

The 600M clock in the fabric is not the real reference, replace it with
a 125M clock which is the correct value for the icicle kit. Rename the
msspllclk node to mssrefclk since this is now the input to, not the
output of, the msspll clock. Control of the msspll clock has been moved
into the clock configurator, so add the register range for it to the clk
configurator. Finally, add a new output of the clock config block which
will provide the 1M reference clock for the MTIMER and the rtc.

Fixes: 528a5b1f ("riscv: dts: microchip: add new peripherals to icicle kit device tree")
Fixes: 0fa6107e

 ("RISC-V: Initial DTS for Microchip ICICLE board")
Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220413075835.3354193-10-conor.dooley@microchip.com
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>