drm/amdgpu/sdma5.2: init engine reset mutex

Missing the mutex init.

Fixes: 47454f2 ("drm/amdgpu: Register the new sdma function pointers for sdma_v5_2")
Reviewed-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit ea685ff)

Author: alexdeucher

drivers/gpu/drm/amd/amdgpu/sdma_v5_2.c

@@ -1318,6 +1318,7 @@ static int sdma_v5_2_sw_init(struct amdgpu_ip_block *ip_block)
 	}
 
 	for (i = 0; i < adev->sdma.num_instances; i++) {
+		mutex_init(&adev->sdma.instance[i].engine_reset_mutex);
 		adev->sdma.instance[i].funcs = &sdma_v5_2_sdma_funcs;
 		ring = &adev->sdma.instance[i].ring;
 		ring->ring_obj = NULL;