drm/amd/amdgpu/amdgpu_ih: Update 'amdgpu_ih_decode_iv_helper()'s function header

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c:220: warning: Function parameter or member 'ih' not described in 'amdgpu_ih_decode_iv_helper'
 drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c:220: warning: Function parameter or member 'entry' not described in 'amdgpu_ih_decode_iv_helper'

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -209,6 +209,8 @@ int amdgpu_ih_process(struct amdgpu_device *adev, struct amdgpu_ih_ring *ih)
  * amdgpu_ih_decode_iv_helper - decode an interrupt vector
  *
  * @adev: amdgpu_device pointer
+ * @ih: ih ring to process
+ * @entry: IV entry
  *
  * Decodes the interrupt vector at the current rptr
  * position and also advance the position for for Vega10