ath5k: support LEDs on Acer Aspire One netbook

Add vendor ID for Foxconn and use it to set the ath5k LED gpio and
polarity for Acer branded laptops.

base.c:
Changes-licensed-under: 3-Clause-BSD

Reported-by: Maxim Levitsky <maximlevitsky@gmail.com>
Tested-by: Maxim Levitsky <maximlevitsky@gmail.com>
Tested-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>