wifi: wilc1000: Clean up usage of wilc_get_chipid()

Reduce the use of wilc_get_chipid(), use cached chip ID wherever
possible. Remove duplicated partial chip ID read implementations
from the driver. Update wilc_get_chipid() to always read the chip
ID out of the hardware and update the cached chip ID, and make it
return a proper return value instead of a chipid. Call wilc_get_chipid()
early to make the cached chip ID available to various sites using
is_wilc1000() to access the cached chip ID.

Reviewed-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20241004114551.40236-2-marex@denx.de