[WCNCR00155733] misc: Refactor iwpriv wlanx stat command

[Description]
Refactor iwpriv stat information format
 - Add Last RX data RSSI, TX response RSSI, Beacon RSSI
 - Support show statistic by group
 - Show two band stat only if DBDC enable
 - replace snprintf to scnprintf in case of using \
   return length to check buffer size
 - Refine stat display format

Change-Id: I67f05916ec53d6a669ed92e9b24f28a0567680a0
Signed-off-by: ted huang <ted.huang@mediatek.com>
CR-Id: WCNCR00155733
Feature: misc
3 files changed