unix: remove dragonfly/386 from mkall.sh

dragonfly/386 isn't a valid GOOS/GOARCH pair and there are no generated
files for this pair in x/sys/unix.

Follows CL 79675 which did the same for syscall.

Change-Id: Ie70937b464fa911a43c26515bcac1c03740dc1fe
Reviewed-on: https://go-review.googlesource.com/79676Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/mkall.sh

@@ -80,12 +80,6 @@ darwin_arm64)
 	mksysnum="./mksysnum_darwin.pl $(xcrun --show-sdk-path --sdk iphoneos)/usr/include/sys/syscall.h"
 	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
 	;;
-dragonfly_386)
-	mkerrors="$mkerrors -m32"
-	mksyscall="./mksyscall.pl -l32 -dragonfly"
-	mksysnum="curl -s 'http://gitweb.dragonflybsd.org/dragonfly.git/blob_plain/HEAD:/sys/kern/syscalls.master' | ./mksysnum_dragonfly.pl"
-	mktypes="GOARCH=$GOARCH go tool cgo -godefs"
-	;;
 dragonfly_amd64)
 	mkerrors="$mkerrors -m64"
 	mksyscall="./mksyscall.pl -dragonfly"