MAINTAINERS: update the entry for the BRCM80211 driver

This time with Signed-off-by ...

Removed Nohee, added Roland, Arend and Dowan.  Changes were previously made
to drivers/staging/brcm80211{README,TODO}, but MAINTAINERS was missed.

Signed-off-by: Henry Ptasinski <henryp@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>