m68k: emu: Mark version[] __maybe_unused

m68k: emu: Mark version[] __maybe_unused

When building with W=1:

    arch/m68k/emu/nfeth.c:42:19: warning: ‘version’ defined but not used [-Wunused-const-variable=]
       42 | static const char version[] =
	  |                   ^~~~~~~

Fix this while obeying the wishes of the original copyright holders by
marking version[] with __maybe_unused.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/051731639b4c8e296ec4017595051885cc551c23.1694613528.git.geert@linux-m68k.org