staging: rtl8192e: Use standard function in rtllib_process_probe_response()

staging: rtl8192e: Use standard function in rtllib_process_probe_response()

Replace proprietary is_beacon() with ieee80211_is_beacon() and
proprietary "WLAN_FC_GET_STYPE(frame_ctl) == RTLLIB_STYPE_PROBE_RESP"
with standard function to increase readability.

Signed-off-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/ad24a52c045d6638103f4263b811c87d18cb3e97.1694546300.git.philipp.g.hortmann@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>