regulator: dt-bindings: samsung,s5m8767: add missing op_mode to bucks

While converting bindings to dtschema, the buck regulators lost
"op_mode" property.  The "op_mode" is a valid property for all
regulators (both LDOs and bucks), so add it.

Reported-by: Rob Herring <robh@kernel.org>
Fixes: fab58deb ("regulator: dt-bindings: samsung,s5m8767: convert to dtschema")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20211206124306.14006-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Mark Brown <broonie@kernel.org>