Removing splxxx functions

From: Warner Losh <imp_at_bsdimp.com>
Date: Sun, 11 Sep 2022 23:25:31 UTC
I intend to remove all the splxxx functions.

Firewire, syscons, smbfs and tpm are the only things that use them.

I plan on copying the function definitions to relevant header files... Or
just deleting the function calls since they've been a nop now just shy of
two decades (depending on how you count things).

I'll leave it to others to decide if any of these should be deprecated in a
separate thread.

Comments?

Warner