qcacmn: Add new attribute for roam reason

Currently, there is no attribute to get information for roam reason.

Atrribute QCA_WLAN_VENDOR_ATTR_ROAM_AUTH_REASON is added in
QCA_NL80211_VENDOR_SUBCMD_KEY_MGMT_ROAM_AUTH command to inform
the roam reason. An enum qca_roam_reason is defined for the valid
values of the QCA_WLAN_VENDOR_ATTR_ROAM_AUTH_ROAM_REASON.

Change-Id: I7f51e1c0905840235098600530bb027f6badb76e
CRs-Fixed: 2425898