nir/validate: Validate that bit sizes and components always match

nir/validate: Validate that bit sizes and components always match

We've always required bit sizes to match but the rules for number of
components have been a bit loose.  You've never been allowed to source
from something with less components than you consume, but more has
always been fine.  This changes the validator to require that they match
exactly.  The fact that they don't always match has been a source of
confusion in NIR for quite some time and it's time we got rid of it.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>