cva6.py : Disable compressed instruction when 'disable_compressed_instr=1'

Created by: AyoubJalali

The cva6.py script use the YAML description to generate random tests, the problem here in the compressed instructions, actually these instructions are active by default, so to disable these instructions we should add an option in the YAML description (disable_compressed_instr=1), but in the cva6.py disable the compressed instructions when it detect the string disable_compressed_instr only, but what if we passed to disable_compressed_instr=0, that's means the C extension still active, so we need to modify the condition to disable compered inst only when disable_compressed_instr=1.