arm64: dts: ti: iot2050: Factor out enabling of USB3 support

Already simplifies the existing code by avoid the switch back in the m2
variant to what k3-am65-main.dtsi provided as base.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Link: https://lore.kernel.org/r/51d9be5ddbf74f90bc915ab5473b9ea9a4b0cdf7.1707463401.git.jan.kiszka@siemens.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>