RPI: Add memory map for bcm2711

Define the memory map for the BCM2711 based on the dt configuration
available in the Raspberry Pi kernel fork.

Signed-off-by: Andrei Gherzan <andrei@balena.io>
[mb: BCM2838 -> BCM2711]
Signed-off-by: Matthias Brugger <mbrugger@suse.com>