ntt: Extend ntt_compile::addr_declared and ntt_compile::addr_reg

ntt: Extend ntt_compile::addr_declared and ntt_compile::addr_reg

This was identified by Coverity.  4bb9c0a28a5 added uses of a third
address register, but the arrays for tracking address registers only
have two slots.

Add back a version of the assertion from before 4bb9c0a28a5 to help
prevent future problems.  I don't think any drivers that would hit
this path use NIR-to-TGSI yet, so it may be moot.

Reviewed-by: Matt Turner <mattst88@gmail.com>
CID: 1496942
CID: 1496944
Fixes: 4bb9c0a28a5 ("nir_to_tgsi: Use the same address reg mappings as GLSL-to-TGSI did.")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14487>