also enable it on all dependencies (where available).
this is needed because in a next commit we'll add code to
`embassy-hal-internal` which uses the feature in a macro, as it expects
`defmt` to be optional in all embassy HALs. this was the only HAL where
that wasn't the case.
note that this is a breaking change for consumers! if you wish to use
`defmt` in `embassy-nxp` you now need to enable the feature.
