brcmfmac: initialize escan function pointer during scheduled scan

brcmfmac: initialize escan function pointer during scheduled scan

For scheduled scan results the driver does a escan to obtain BSS
details from the firmware. However, the escan uses a dynamically
determined function. This needs to be set appropriately when handling
scheduled scan results to avoid NULL pointer access.

Reviewed-by: Franky Lin <[email protected]>
Reviewed-by: Hante Meuleman <[email protected]>
Reviewed-by: Pieter-Paul Giesberts <[email protected]>
Reviewed-by: Daniel (Deognyoun) Kim <[email protected]>
Signed-off-by: Arend van Spriel <[email protected]>
Signed-off-by: John W. Linville <[email protected]>