AP_DDS: Change the comparison of float value zero to IS_XXXX #721

Job	Run time
build (stm32f7, chibios, 10)	14m 2s
build (stm32h7, chibios, 10)	13m 12s
build (fmuv2-plane, chibios, 10)	11m 49s
build (periph-build, chibios, 10)	9m 40s
build (iofirmware, chibios, 10)	3m 51s
build (CubeOrange-bootloader, chibios, 10)	8m 3s
build (fmuv3-bootloader, chibios, 10)	2m 55s
build (revo-bootloader, chibios, 10)	3m 17s
build (stm32h7-debug, chibios, 10)	8m 36s
build (fmuv3, chibios, 10)	14m 59s
build (revo-mini, chibios, 10)	12m 0s
build (MatekF405-Wing, chibios, 10)	12m 9s
build (CubeOrange-ODID, chibios, 10)	9m 40s
build (CubeRedPrimary-bootloader, chibios, 10)	3m 27s
build (configure-all, chibios, 10)	12m 45s
build (build-options-defaults-test, chibios, 10)	23m 45s
build (signing, chibios, 10)	9m 19s
build (CubeOrange-PPP, chibios, 10)	8m 30s
build (CubeRed-EKF2, chibios, 10)	8m 9s
build (SOHW, chibios, 10)	11m 58s
build (Pixhawk6X-PPPGW, chibios, 10)	3m 48s
build (new-check, chibios, 10)	14m 1s
	3h 39m 55s

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