hw/display/milkymist-tmu2: Move inlined code from header to source

Move the complexity of milkymist_tmu2_create() into the
source file. Doing so we avoid to include the X11/OpenGL
headers in all LM32 devices, and we also avoid the duplicate
declaration of glx_fbconfig_attr[] (it is already declared
in hw/display/milkymist-tmu2.c).
Since TYPE_MILKYMIST_TMU2 is now accessible, use it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190130120005.23123-5-philmd@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index 234e5c4..37ceda4 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -185,6 +185,7 @@
 F: hw/lm32/
 F: hw/*/lm32_*
 F: hw/*/milkymist-*
+F: include/hw/display/milkymist_tmu2.h
 F: include/hw/char/lm32_juart.h
 F: include/hw/lm32/
 F: tests/tcg/lm32/