When building with W=1:

    arch/m68k/sun3/config.c:123:13: warning: no previous prototype for ‘config_sun3’ [-Wmissing-prototypes]
      126 | void __init config_sun3(void)
	  |             ^~~~~~~~~~~
    arch/m68k/sun3x/config.c:42:13: warning: no previous prototype for ‘config_sun3x’ [-Wmissing-prototypes]
       42 | void __init config_sun3x(void)
	  |             ^~~~~~~~~~~~

Fix this by including <asm/config.h>

Fixes: 91d7b75a ("m68k: Add asm/config.h")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/b9178e864d6c5e06c177d53bc4cce6d689f94d78.1694613528.git.geert@linux-m68k.org