wilc1000: use correct write command sequence in wilc_spi_sync_ext()

Instead of using double read for the same register, use the write register
command after the read command.
The correct sequence is to use the read value in write command instead of
reading the same register again.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210916164902.74629-11-ajay.kathat@microchip.com