[buffer] transcode() to utf16le is broken

[trevnorris]

• Version: v7.2.0
• Platform: Linux
• Subsystem: buffer

Examples of brokenness:

// note: this works properly if `fromEnc` is 'utf8'
buffer.transcode(Buffer.from('hi', 'ascii'), 'ascii', 'utf16le')
// expect: <Buffer 68 00 69 00>
// get:    <Buffer 68 00 69 00 00 00 00 00 60 db 18 c6 fe 7f 00 00>

buffer.transcode(Buffer.from('hi', 'latin1'), 'latin1', 'utf16le')
// expect: <Buffer 68 00 69 00>
// get:    <Buffer 68 00 69 00 00 00 00 00 60 db 18 c6 fe 7f 00 00>

buffer.transcode(Buffer.from('\u00e4', 'latin1'), 'latin1', 'utf16le')
// expect: <Buffer e4 00>
// get:    <Buffer e4 00 00 00 fe 7f 00 00>

Not sure when I'll have time to look into this.

/cc @jasnell

[trevnorris]

Is this possibly happening b/c it's actually converting to UCS2 and not proper UTF16-LE?