sys/dts/arm/ufs.dts: fix compile error

Fix compile error due to the include file am33xx.dtsi has been moved.
The Linux device-tree archive has split the general directory
(ARM/ARM64...) into vendor specific subdirectories since Linux 6.5.

Reviewed by: kp
Approved by: manu (mentor)
Differential revision: https://reviews.freebsd.org/D53894