git.sh: revert modification to for loop

i tried to be clever with this one, but it just made
the script exit with an error.

revert back to the old check (check whether one of
either repo or repo backup is set)

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/git.sh

@@ -118,8 +118,10 @@ fetch_submodule()
 	    $err "! . $mcfgdir/module.cfg"
 
 	for xt in repo file; do
-		eval "[ -n \"\$sub$xt\$sub${xt}_bkup\" ] && st=\"\$st \$xt\""
+		_seval="if [ -n \"\$sub$xt\" ] || [ -n \"\$sub${xt}_bkup\" ]"
+		eval "$_seval; then st=\"\$st \$xt\"; fi"
 	done
+
 	st="${st# }" && [ "$st" = "repo file" ] && $err "$mdir: repo+file"
 
 	[ -z "$st" ] && return 0 # subrepo/subfile not defined