hwdef: remove non-ublox GPSes from MatekL431-Periph

Saves enough flash to get it building again (11K now free). These
backends are default for other boards and so are built in CI.

Author: tpwrules

libraries/AP_HAL_ChibiOS/hwdef/MatekL431-Periph/hwdef.dat

@@ -23,6 +23,10 @@ define HAL_PERIPH_GPS_PORT_DEFAULT 2
 # allow for F9P GPS modules with moving baseline
 define GPS_MOVING_BASELINE 1
 
+# restrict backends available to save flash (i.e. only UBLOX)
+define AP_GPS_NOVA_ENABLED 0
+define AP_GPS_SBF_ENABLED 0
+define AP_GPS_GSOF_ENABLED 0
 
 # ---------------------- COMPASS ---------------------------
 define HAL_PERIPH_ENABLE_MAG