openfimg: Fix various compiler warnings

Extra checks have been triggered by -pedantic flag.

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: Minor clean-ups of code generator

Signed-off-by: Tomasz Figa <tomasz.figa@gmail.com>
openfimg: Implement few more TGSI opcodes

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