MAINTAINERS: Broadcom internal lists aren't maintainers

Convert the broadcom internal list M: and L: entries to R: as
exploder email addresses are neither maintainers nor mailing lists.

Reorder the entries as necessary.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>