brcmfmac: rework pointer trickery in brcmf_proto_bcdc_query_dcmd()

The variable info is assigned to point to bcdc->msg[1], which is the
same as pointing to bcdc->buf. As that is what we want to access
make it clear by fixing the assignment. This also avoid out-of-bounds
errors from static analyzers are bcdc->msg[1] is not in the structure
definition.

Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>