arm64: dts: k3-am654-base-board: Add I2C GPIO expander @ 0x38

The AM654 base board has a TCA9554/PCA9554-type GPIO expander on the
wkup_i2c0 bus at address 0x38 that is used to detect the presence of
daughter cards.  Add a respective DTS description of this expander
to enable its use.

Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>