usb: dwc3: drd: Defer probe if extcon device is not found

In case the "linux,extcon-name" property is defined but device itself is not ready, defer the probe.

Cc Felipe Balbi <[email protected]>

Signed-off-by Andy Shevchenko <[email protected]>

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This is a missed part of the v2 [1] of the commit 268784ba14a7

("usb: dwc3: drd: Add support for DR detection through extcon")

which seems to be v1 mistakenly applied.

Greg, it would be good to have this appended to v5.0 release, if it's not too late.

[1]: https://patchwork.kernel.org/patch/10684311/