rpi: use constant "unknown board" DT filename

To simplify support for new SoCs, just use a constant filename
for the unknown case. In practice this case shouldn't be hit anyway, so
the filename isn't relevant, and certainly doesn't need to differentiate
between SoCs. If a user has an as-yet-unknown board, they can override
this value in the environment anyway.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

board/raspberrypi/rpi/rpi.c

@@ -99,11 +99,7 @@ struct rpi_model {
 
 static const struct rpi_model rpi_model_unknown = {
 	"Unknown model",
-#ifdef CONFIG_BCM2836
-	"bcm2836-rpi-other.dtb",
-#else
-	"bcm2835-rpi-other.dtb",
-#endif
+	"bcm283x-rpi-other.dtb",
 	false,
 };