wilc1000: Convert static "chipid" variable to device-local variable

Move "chipid" variable into the per-driver structure so the code
doesn't break if more than one wilc1000 module is present.

Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211221210538.4011227-1-davidm@egauge.net