minigbm: use struct vma for (*bo_map)/(*bo_unmap) callbacks

This sets better expectations for what we expect from the
backends.

BUG=chromium:764871
TEST=mmap_test

Change-Id: I7fb815b58fae8e9fbd73bf7c0263c7db44488844
Reviewed-on: https://chromium-review.googlesource.com/770519
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Joe Kniss <djmk@google.com>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
diff --git a/i915.c b/i915.c
index 965f62d..0b30703 100644
--- a/i915.c
+++ b/i915.c
@@ -404,7 +404,9 @@
 					 uint32_t format, const uint64_t *modifiers, uint32_t count)
 {
 	static const uint64_t modifier_order[] = {
-		I915_FORMAT_MOD_Y_TILED, I915_FORMAT_MOD_X_TILED, DRM_FORMAT_MOD_LINEAR,
+		I915_FORMAT_MOD_Y_TILED,
+		I915_FORMAT_MOD_X_TILED,
+		DRM_FORMAT_MOD_LINEAR,
 	};
 	uint64_t modifier;
 
@@ -445,7 +447,7 @@
 	return 0;
 }
 
-static void *i915_bo_map(struct bo *bo, struct mapping *mapping, size_t plane, uint32_t map_flags)
+static void *i915_bo_map(struct bo *bo, struct vma *vma, size_t plane, uint32_t map_flags)
 {
 	int ret;
 	void *addr;
@@ -489,7 +491,7 @@
 		return addr;
 	}
 
-	mapping->vma->length = bo->total_size;
+	vma->length = bo->total_size;
 	return addr;
 }