rtlwifi: rtl8723ae: Convert driver to use new rtl_phy_scan_operation_backup() routine

Now that rtl_phy_scan_operation_backup() exists, convert rtl8723ae to use it.
Routine rtl8723ae_phy_scan_operation_backup() is no longer used and is removed.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>