arm: mach-k3: j784s4: Fix MCU_CLKOUT0 parent clock mux

arm: mach-k3: j784s4: Fix MCU_CLKOUT0 parent clock mux

MCU_CLKOUT0 output can be driven by two different clock inputs:
one at 25 MHz and another at 50 MHz. Currently, the 25 MHz input
clock is not selectable due to a duplication of the 50 MHz clock input
in the mux configuration. This commit corrects the parent clock mux
configuration, making the 25 MHz input clock selectable.

Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
Reviewed-by: Bryan Brattlof <bb@ti.com>