Fixed if (token)

Reworked to rebase cleanly on other series changes

Moved sc->trs allocation earlier

Made scmi_detach static

Removed the extres header references

Using mallocarray and dropping empty interface method

Removed needless checks on malloc, using mallocarray

Removed needless malloc checks

Removed check on malloc return value

Removed needless empty interface methods

Removed __FBSDID

Removed the __FBSDID

Thanks for the review @bryanv.
Regarding:

In D43045#989478, @andrew wrote:

Could you use unr(9), the kernel unit number allocator, to allocate the tokens?

In D43044#989468, @andrew wrote:

The attach and detach functions that just call smci_attach and smci_detach could be removed. If a driver doesn't implement a method, but the parent does then the parent implementation will be used.

SCMI: Add support for multiple transports and add VirtIO/SMC transports