SITL: correct valgrind failure in SIM_GPS_SBP2 #39053

Job	Run time
build (stm32f7, chibios, 10)	3m 51s
build (stm32h7, chibios, 10)	3m 46s
build (fmuv2-plane, chibios, 10)	1m 51s
build (periph-build, chibios, 10)	3m 58s
build (iofirmware, chibios, 10)	1m 36s
build (CubeOrange-bootloader, chibios, 10)	51s
build (fmuv3-bootloader, chibios, 10)	51s
build (revo-bootloader, chibios, 10)	51s
build (stm32h7-debug, chibios, 10)	2m 26s
build (fmuv3, chibios, 10)	5m 0s
build (revo-mini, chibios, 10)	3m 55s
build (MatekF405-Wing, chibios, 10)	4m 3s
build (CubeOrange-ODID, chibios, 10)	2m 31s
build (CubeRedPrimary-bootloader, chibios, 10)	1m 13s
build (configure-all, chibios, 10)	9m 54s
build (build-options-defaults-test, chibios, 10)	7m 24s
build (signing, chibios, 10)	3m 5s
build (CubeOrange-PPP, chibios, 10)	2m 1s
build (SOHW, chibios, 10)	3m 19s
build (Pixhawk6X-PPPGW, chibios, 10)	1m 11s
	1h 3m 37s

Provide feedback