dt-bindings: phy: usb-snps-femto-v2: Add regulator entries to example

Fix errors reported by dt_binding_check, due to missing required
regulators in the example node.

Fixes: f06b9fc9 ("dt-bindings: phy: Add binding for qcom,usb-snps-femto-v2")
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Reported-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1588753589-22673-1-git-send-email-wcheng@codeaurora.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>