drm: increase drm mmap_range size to 1TB

After patch "drm: Use the same mmap-range offset and size for GEM and
TTM", application failed to create bo of system memory because drm
mmap_range size decrease to 64GB from original 1TB. This is not big
enough for applications. Increase the drm mmap_range size to 1TB.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190417221507.933-1-Philip.Yang@amd.com
(cherry picked from commit 96354b5ca4)

include/drm/drm_vma_manager.h

@@ -35,7 +35,7 @@
  */
 #if BITS_PER_LONG == 64
 #define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFFUL >> PAGE_SHIFT) + 1)
-#define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFFUL >> PAGE_SHIFT) * 16)
+#define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFFUL >> PAGE_SHIFT) * 256)
 #else
 #define DRM_FILE_PAGE_OFFSET_START ((0xFFFFFFFUL >> PAGE_SHIFT) + 1)
 #define DRM_FILE_PAGE_OFFSET_SIZE ((0xFFFFFFFUL >> PAGE_SHIFT) * 16)