wifi: wilc1000: Keep slot powered on during suspend/resume

The WILC3000 can suspend and enter low power state. According to local
measurements, the WILC3000 consumes the same amount of power if the slot
is powered up and WILC3000 is suspended, and if the WILC3000 is powered
off. Use the former option, keep the WILC3000 powered up as that allows
for things like WoWlan to work.

Note that this is tested on WILC3000 only, not on WILC1000 .

Signed-off-by: Marek Vasut <marex@denx.de>
Tested-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20240926195113.2823392-1-marex@denx.de