drivers: wifi: winc1500: Fix wifi module so that it is not held in reset.

The "nm_bsp_reset" is used to apply a hard reset to the WINC board by
setting CHIP_EN and RESET_N signals low,then after specific delay
the function will put CHIP_EN high then RESET_N high.
reset-gpio is however defined as active low , causing this function
to hold the wifi module in reset.

Signed-off-by: Andreas Ålgård <aal@ixys.no>