During implementation of commit 257b119c2d ("QCA vendor attribute of
update roaming cached statistics info") some deficiencies were noted as
listed below, so fix them. Since these are pre-implementation changes,
no ABI breakage is introduced.
1) Change all RSSI values to be signed values.
2) Add enums for scan type and dwell type instead of documenting
their values with comments
3) Add missing QCA_ROAM_REASON_STA_KICKOUT to enum qca_roam_reason
Signed-off-by: Chunquan Luo <quic_chunquan@quicinc.com>