make: Use C flags for C++ as default

In case a BSP selects special CFLAGS_OPTIMIZE_V flags then they will be
also used for CXXFLAGS_OPTIMIZE_V automatically for example.
framebuffer: Add and use FRAMEBUFFER_DEVICE_0_NAME
mouse: Include missing header file
libchip/serial: Add const qualifier
bsps/arm: Add PL111 support
bsps/arm: Add PL050 support