Add check to consider band in enabling connection_vht flag

Add check to consider band in enabling connection_vht flag

connection_vht flag was set to true when both Association Request and
Response frame IEs have VHT capability. Thus all devices that have
support for the vendor specific partial VHT support in the 2.4 GHz band
were also being reported as VHT capable. However, IEEE Std 802.11ac-2013
defines VHT STA to operate in frequency bands below 6 GHz excluding the
2.4 GHz band.

Do not set connection_vht when the operating band is 2.4 GHz. This
avoids reporting wifi_generation 5 on the 2.4 GHz band and reserves the
generation value 5 for full VHT as defined in the IEEE 802.11 standard.

Signed-off-by: Veerendranath Jakkam <vjakkam@codeaurora.org>