hostapd: Fix Max SP Length derivation from QoS Info

Hostapd provides QoS info of the STA (Service Period & AC mask) to the
kernel during wpa_driver_nl80211_sta_add call. Bit 5 and Bit 6 of QoS
info represents the Max SP length. Fix an issue in the code to fetch the
Max SP by shifting right the QoS info by value WMM_QOSINFO_STA_SP_SHIFT.
(operator ">" is replaced with ">>" operator).

Signed-off-by: Srinivasan <srinivasanb@posedge.com>