brcmfmac: add creating station interface support

With RSDB device, it is able to control two station interfaces
concurrently. So we add creating station interface support and
allow user to create it via cfg80211.

Signed-off-by: Wright Feng <wright.feng@cypress.com>
Signed-off-by: Chi-hsien Lin <chi-hsien.lin@infineon.com>
Signed-off-by: Ian Lin <ian.lin@infineon.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220929050614.31518-2-ian.lin@infineon.com