drm/amdgpu: include pagemap.h for release_pages()

Fixes: 5ae0283e ("drm/amdgpu: Add userptr support for KFD"
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c

@@ -23,6 +23,7 @@
 #define pr_fmt(fmt) "kfd2kgd: " fmt
 
 #include <linux/list.h>
+#include <linux/pagemap.h>
 #include <linux/sched/mm.h>
 #include <drm/drmP.h>
 #include "amdgpu_object.h"