clk: clk-axi-clkgen: fix fpfd_max frequency for zynq

clk: clk-axi-clkgen: fix fpfd_max frequency for zynq

The fpfd_max frequency should be set to 450 MHz instead of 300 MHz.
Well, it actually depends on the platform speed grade but we are being
conservative for ultrascale so let's be consistent. In a following
change we will set these limits at runtime.

Fixes: 0e646c52cf0e ("clk: Add axi-clkgen driver")
Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20250519-dev-axi-clkgen-limits-v6-1-bc4b3b61d1d4@analog.com
Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>