Revert "openfimg: compiler: Refactor variables_defined()"

This reverts commit c025b8b0feaf27c6e1c3705f7929dd7b489555c0.
openfimg: compiler: Fix variables_defined()

Finding variables defined by nodes is reimplemented to fix typos present
in related paper that was source of the idea.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Simplify copying of renames array

A simple memcpy is enough.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Create local copy of renames array for repeats too

This is how it is described in the paper, but the pseudocode does not do
it, which I believe is a mistake.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Add missing memsets

All fields of instruction template struct must be initialized so unused
ones must be zeroed.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Change invalid swizzle into assertion

It is not a client error, but internal driver failure.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Print processing stage before dumping SSA AST

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>