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 <[e-mail]>
Reviewed-by: Franky (Zhenhui) Lin <[e-mail]>
Reviewed-by: Daniel (Deognyoun) Kim <[e-mail]>
Reviewed-by: Pieter-Paul Giesberts <[e-mail]>
Signed-off-by: Arend van Spriel <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/brcm80211/brcmutil/d11.c

···
 	if (ch->bw == BRCMU_CHAN_BW_20)
 		ch->sb = BRCMU_CHAN_SB_NONE;
 
+	ch->chspec = 0;
 	brcmu_maskset16(&ch->chspec, BRCMU_CHSPEC_CH_MASK,
 			BRCMU_CHSPEC_CH_SHIFT, ch->chnum);
 	brcmu_maskset16(&ch->chspec, BRCMU_CHSPEC_D11N_SB_MASK,
···
 	brcmu_maskset16(&ch->chspec, BRCMU_CHSPEC_D11N_BW_MASK,
 			0, d11n_bw(ch->bw));
 
-	ch->chspec &= ~BRCMU_CHSPEC_D11N_BND_MASK;
 	if (ch->chnum <= CH_MAX_2G_CHANNEL)
 		ch->chspec |= BRCMU_CHSPEC_D11N_BND_2G;
 	else