clk: ast2600: Add FSI parent clock with correct rate

In order to calculate correct FSI bus clocks, the FSI clock must
correctly calculate the rate from the parent (APLL / 4).

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Link: https://lore.kernel.org/r/20240215220759.976998-3-eajames@linux.ibm.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>