drm/amd/amdgpu/amdgpu_ring: Fix misnaming of param 'max_dw'

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

 drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c:168: warning: Function parameter or member 'max_dw' not described in 'amdgpu_ring_init'
 drivers/gpu/drm/amd/amdgpu/amdgpu_ring.c:168: warning: Excess function parameter 'max_ndw' description in 'amdgpu_ring_init'

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: Sumit Semwal <sumit.semwal@linaro.org>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.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_ring.c

@@ -154,7 +154,7 @@ void amdgpu_ring_undo(struct amdgpu_ring *ring)
  *
  * @adev: amdgpu_device pointer
  * @ring: amdgpu_ring structure holding ring information
- * @max_ndw: maximum number of dw for ring alloc
+ * @max_dw: maximum number of dw for ring alloc
  * @irq_src: interrupt source to use for this ring
  * @irq_type: interrupt type to use for this ring
  * @hw_prio: ring priority (NORMAL/HIGH)