Move the Special opcodes helpers to tcg/sysemu/special_helper.c.

Since mips_io_recompile_replay_branch() is set as
CPUClass::io_recompile_replay_branch handler in cpu.c,
we need to declare its prototype in "tcg-internal.h".

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210428170410.479308-24-f4bug@amsat.org>