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

arch/m68k/emu/nfeth.c

@@ -39,7 +39,7 @@ enum {
 #define MAX_UNIT	8
 
 /* These identify the driver base version and may not be removed. */
-static const char version[] =
+static const char version[] __maybe_unused =
 	KERN_INFO KBUILD_MODNAME ".c:v" DRV_VERSION " " DRV_RELDATE
 	" S.Opichal, M.Jurik, P.Stehlik\n"
 	KERN_INFO " http://aranym.org/\n";