MAINTAINERS: corrected bcm2835 search

Corrected bcm2835 maintainer info by using N: to specify any files with
bcm2835 in are directed to the proper maintainer.
Also corrected minor mispelling of ARCHITECTURE in 2 comment locations.

Signed-off-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Olof Johansson <olof@lixom.net>