fs: fix misplaced errors in fs.symlinkSync

The ctx.error is supposed to be handled in fs.readlinkSync,
but was handled in fs.symlinkSync by mistake.

Also fix the error number check in readlink to be consistent
with SYNC_CALL.

PR-URL: https://github.com/nodejs/node/pull/18548
Refs: https://github.com/nodejs/node/pull/18348


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>