audio/musicpd: drop unused MPD_CLANG_LD after 620968a43a5f

Builds fine on armv6 at least with LLD 12.0.1. Since FreeBSD >= 12.0
armv6 is deprecated in favor of armv7, anyway.

$ objdump -D $(which musicpd) | fgrep -w -e movt -e movw; echo Exit $?
Exit 1