openfimg: compiler: Work around a heisenbug

Single stepping the code leads to a single assembly instruction
(compiled for x86) which looks fine, but with offset == 3 gives '{'
instead of 'w' after stepping through it...

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Fix handling of operations without dst in liveness

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: compiler: Silence the noisy register allocator

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