drm/vgem: replace idr_init() by idr_init_base()

idr_init() uses base 0 which is an invalid identifier. The new function
idr_init_base allows IDR to set the ID lookup from base 1. This avoids
all lookups that otherwise starts from 0 since 0 is always unused.

References: commit 6ce711f27500 ("idr: Make 1-based IDRs more efficient")

Signed-off-by: Deepak R Varma <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/20201105173646.GA41732@localhost

drivers/gpu/drm/vgem/vgem_fence.c

···
 int vgem_fence_open(struct vgem_file *vfile)
 {
 	mutex_init(&vfile->fence_mutex);
-	idr_init(&vfile->fence_idr);
+	idr_init_base(&vfile->fence_idr, 1);
 
 	return 0;
 }