drivers: wifi: Fix QSPI clock dividers

For less than 32MHz using HFCLK192M, /2 divider should be used and only
for Anamoly159 /1 divider should be used.

Without this fix 8MHz clock in DTS uses 16MHz clock.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>