arm64: dts: ti: k3-am67a-beagley-ai: Add bootph for main_gpio1

main_gpio1 controls the voltage for the SDcard from 3.3v to 1.8v.
This is required for proper operation of SDcard through various boot
stages.

Reviewed-by: Udit Kumar <u-kumar1@ti.com>
Link: https://lore.kernel.org/r/20250411203950.2859356-1-nm@ti.com


Signed-off-by: Nishanth Menon <nm@ti.com>