disas/nanomips: Remove disasm methods from class

disas/nanomips: Remove disasm methods from class

NMD class methods with the disassembly_function type like
NMD::ABS_D, NMD::ABS_S, etc. are removed from the class. They're now
declared global static functions. Therefore, typedef of the function
pointer, disassembly_function is defined outside of the class.

Now that disassembly_function type functions are not part of the NMD
class we can't access them using the this pointer. Thus, the use of
the this pointer has been deleted.

Signed-off-by: Milica Lazarevic <milica.lazarevic@syrmia.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220912122635.74032-8-milica.lazarevic@syrmia.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>