driver: wifi: siwx91x: Fix scan params error for 5Ghz band

- Rejected non 2.4GHz band channels from Wifi-Scan.
- Overrode the WIFI_MGMT_SCAN_CHAN_MAX_MANUAL parameter to 50.
- Added check for wrong interface and invalid states

Signed-off-by: Nitin Pandey <nitin.pandey@silabs.com>