m68k: sun3x: Fix signature of sun3_leds()

The sun3_leds() implementation for Sun3 in arch/m68k/sun3/leds.c, and
the prototype in arch/m68k/sun3/sun3ints.c take an "unsigned char", not
an "int".  Align the dummy implementation for Sun3x with the Sun3
variant and the common caller.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/5214afb67eac58b8adae5710aea0980c2644ff24.1694613528.git.geert@linux-m68k.org