drm: Kbuild: add admgpu_drm.h to the installed headers

Signed-off-by: NGabriel Laskar <gabriel@lse.epita.fr>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Acked-by: NAlex Deucher <alexander.deucher@amd.com>
CC: Emil Velikov <emil.l.velikov@gmail.com>
CC: Mikko Rapeli <mikko.rapeli@iki.fi>

include/uapi/drm/Kbuild

@@ -3,6 +3,7 @@ header-y += drm.h
 header-y += drm_fourcc.h
 header-y += drm_mode.h
 header-y += drm_sarea.h
+header-y += amdgpu_drm.h
 header-y += exynos_drm.h
 header-y += i810_drm.h
 header-y += i915_drm.h