sysutils/u-boot-pandaboard: Remove EOL port

The omap4 boards has been removed from u-boot in 2024.10 release.
For details see commit in u-boot repo
1104cd616fef3111f851f7058511e45c3081f8cf

Approved by: manu (mentor)
Differential revision: https://reviews.freebsd.org/D49876