stand: efi_fmtdev can be reduced to devformat

devformat produces the same output as efi_fmtdev, so just use it to
reduce on the dependencies.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D35924

(cherry picked from commit 1e7a2eb93a527a2f4b22be66788caf50e4ba1f89)