RPi: just use RPI instead of RPI2.

The reason for this change is that RPi2 and RPi3 are compatible, and
hopefully all differences coming up can be resolved without ifdefs but
at runtime.

src/firmware/posix/CMakeLists.txt

@@ -37,7 +37,7 @@ if ("${BOARD}" STREQUAL "eagle" OR ("${BOARD}" STREQUAL "excelsior"))
 			 DEPENDS mainapp
 			 DEST /home/linaro)
 
-elseif ("${BOARD}" STREQUAL "rpi2")
+elseif ("${BOARD}" STREQUAL "rpi")
 
 	add_executable(mainapp
 		${CMAKE_SOURCE_DIR}/src/platforms/posix/main.cpp
@@ -57,7 +57,7 @@ elseif ("${BOARD}" STREQUAL "rpi2")
 			 OS ${OS}
 			 BOARD ${BOARD}
 			 FILES ${CMAKE_CURRENT_BINARY_DIR}/mainapp
-				 ${CMAKE_SOURCE_DIR}/posix-configs/rpi2/mainapp.config
+				 ${CMAKE_SOURCE_DIR}/posix-configs/rpi/mainapp.config
 			 DEPENDS mainapp
 			 DEST /home/pi)