This patch adds mutual inclusion protection for the rpi firmware header.

Cc: Eric Anholt <eric@anholt.net>
Cc: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>