brcmfmac: remove setting IBSS mode when stopping AP

brcmfmac: remove setting IBSS mode when stopping AP

Upon stopping an AP interface the driver disable INFRA mode effectively
setting the interface in IBSS mode. However, this may affect other
interfaces running in INFRA mode. For instance, if user creates and stops
hostap daemon on virtual interface, then association cannot work on
primary interface because default BSS has been set to IBSS mode in
firmware side. The IBSS mode should be set when cfg80211 changes the
interface.

Reviewed-by: Wright Feng <wright.feng@cypress.com>
Signed-off-by: Chi-hsien Lin <Chi-Hsien.Lin@cypress.com>
[kvalo@codeaurora.org: rephased commit log based on discussion]
Signed-off-by: Wright Feng <wright.feng@cypress.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>