WPS: Enforce five second minimum time before AP iteration

WPS: Enforce five second minimum time before AP iteration

Previously, wpa_supplicant was using number of scan iterations
(WPS_PIN_SCAN_IGNORE_SEL_REG = 3) to give some time for finding a WPS AP
with Selected Registrar TRUE before starting to iterate through all WPS
APs. While this works fine in most cases, some drivers may return the
initial three scan results so quickly that the total amount of time is
only couple of seconds in case none of the APs are initially advertising
Selected Registrar TRUE. To give some more time for APs (WPS Registrars)
to become ready, add an additional constraint on the iteration based on
time (WPS_PIN_TIME_IGNORE_SEL_REG = 5 seconds).

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>