WIP: bcm2835: Increase DMA Coherent Pool size to 4M

VCHIQ needs this.
WIP: vc04_services: Videocore VCHIQ

TODO:

0.) Remove userspace knobs

1.) Massive cleanup
WIP: FIXUP: Get rid of global BCM2835 Mailbox device
WIP: ALSA: Add Broadcom BCM2835 sound driver

TODO:

0.) Massive cleanup