brcmutil: assure unused bits are cleared in 11n chanspec
brcmutil: assure unused bits are cleared in 11n chanspec

The firmware channel specification is a bitfield using a
16-bit integer, but only 14 lsb are used. Upon encoding
this value assure all 16 bits are cleared.

Reviewed-by: Hante Meuleman <31ca5aa57e9f47a38c33f2797b138069dfa82656@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <c740ae0f5dfc9bd2203ae1a0d3155a31e94c745d@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <996ffb484be4810f081e1899e9b77a0b6fd6a184@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <d101f7ec36e185d305862a92a05a9a0c1b62aa38@broadcom.com>
Signed-off-by: Arend van Spriel <06447fbe43693466d3293d0b5eaeeb2efd3d7d3a@broadcom.com>
Signed-off-by: John W. Linville <2a53bac7a5d324865ef46ec4c38b2c0fba1456b4@tuxdriver.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs