configs: am67a_beagley_ai*: Use saveddefconfig

configs: am67a_beagley_ai*: Use saveddefconfig

Drop using j722s_evm defconfig since the evm has numerous features that
we do not need on BeagleY-AI platform. As new peripherals get added to
EVM support, we end up having to cleanup after in beagle configurations.

Instead of doing that, just split up BeagleY's configuration
independently out.

NOTE: no cleanup has been done to this configuration to allow for
reproducibility. The cleanups are done in follow on patches

Acked-by: Andrew Davis <afd@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Bryan Brattlof <bb@ti.com>
Reviewed-by: Andrew Davis <afd@ti.com>