ARM: bcm2835: dt: Add Raspberry Pi Model A

This one is essentially the same as revision 2 B board (with the I2S on
P5 header).

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
[anholt: Rebased on bcm2835.dtsi -> bcm283x.dtsi change]
Signed-off-by: Eric Anholt <eric@anholt.net>