ARM: bcm283x: don't always define CONFIG_BCM2835

Currently, CONFIG_BCM2835 is defined for all BCM283x builds and _BCM2836
is defined when building for that SoC. That means there isn't a single
define that means "exactly BCM2835". This will complicate future patches
where BCM2835-vs-anything-else needs to be determined simply.

Modify the code to define one or the other of CONFIG_BCM2835/BCM2836 so
future patches are simpler.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index da4b6ff..1fd7591 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -31,7 +31,7 @@
 };
 
 static const struct pl01x_serial_platdata serial_platdata = {
-#ifdef CONFIG_BCM2836
+#ifndef CONFIG_BCM2835
 	.base = 0x3f201000,
 #else
 	.base = 0x20201000,