clk: socfpga: agilex: fix the parents of the psi_ref_clk

clk: socfpga: agilex: fix the parents of the psi_ref_clk

The psi_ref_clk comes from the C2 node of the main_pll and periph_pll,
not the C3.

Fixes: 80c6b7a0894f ("clk: socfpga: agilex: add clock driver for the Agilex platform")
Cc: stable@vger.kernel.org
Signed-off-by: Kris Chaplin <kris.chaplin@intel.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Link: https://lore.kernel.org/r/20210713144621.605140-1-dinguyen@kernel.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>