Commit e52f3f29 ("ASoC: audio-graph-card: Refactor schema") added an
'allOf' entry, but one is already present in the schema. Multiple keys
is not valid and results in an error:

ruamel.yaml.constructor.DuplicateKeyError: while constructing a mapping
  in "<unicode string>", line 4, column 1
found duplicate key "allOf" with value "[]" (original value: "[]")
  in "<unicode string>", line 262, column 1

Fixes: e52f3f29 ("ASoC: audio-graph-card: Refactor schema")
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Cc: Sameer Pujar <spujar@nvidia.com>
Cc: alsa-devel@alsa-project.org
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201119161848.3379929-1-robh@kernel.orgSigned-off-by: Mark Brown <broonie@kernel.org>