soc: arm: ti_k3: am62x_m4: Lower Initialization level for init

Other drivers like the pinctrl_ti_k3 rely on a fully initialized system.
Move the am62x_init to an earlier stage than PRE_KERNEL_1 to keep both
PRE_KERNEL_{1,2} free for drivers.

Signed-off-by: Daniel Schultz <d.schultz@phytec.de>