qcacmn: Correct RSNXE capability indexes

Currently, RSNXE capability indexes are defined incorrect.
It seems BIT index is misinterpreted. Correct the same as defined
below in spec(IEEE Std 802.11-2020, 9.4.2.241, Table 9-780).

The Extended RSN Capabilities field, except its first 4 bits, is a
bit field indicating the extended RSN capabilities being advertised
by the STA transmitting the element. The length of the Extended
RSN Capabilities field is a variable n, in octets, as indicated by
the first 4 bits in the field.

Also, add a macro to check if the given akm
is WPA/WPA2 i.e. legacy than WPA3.

Change-Id: I3d8eee15f6734b2364628f699b7829a1edb246f0
CRs-Fixed: 3257715