drm/mgag200: Rename mgag200_ttm.c to mgag200_mm.c

The mgag200 driver does not use TTM any longer. Rename the related file
to mgag200_mm.c (as in 'memory management').
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200605135803.19811-5-tzimmermann@suse.de

drivers/gpu/drm/mgag200/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
-mgag200-y   := mgag200_main.o mgag200_mode.o \
-	mgag200_drv.o mgag200_i2c.o mgag200_ttm.o
+mgag200-y   := mgag200_drv.o mgag200_i2c.o mgag200_main.o mgag200_mm.o \
+	       mgag200_mode.o
 
 obj-$(CONFIG_DRM_MGAG200) += mgag200.o

drivers/gpu/drm/mgag200/mgag200_drv.h

@@ -196,6 +196,7 @@ void mgag200_driver_unload(struct drm_device *dev);
 struct mga_i2c_chan *mgag200_i2c_create(struct drm_device *dev);
 void mgag200_i2c_destroy(struct mga_i2c_chan *i2c);
 
+				/* mgag200_mm.c */
 int mgag200_mm_init(struct mga_device *mdev);
 void mgag200_mm_fini(struct mga_device *mdev);