arm: Replace calls to __builtin_vcgt* by <,> in arm_neon.h [PR66791]

gcc/
2020-12-16  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	PR target/66791
	* config/arm/arm_neon.h: Replace calls to __builtin_vcgt* by
	<, > operators in vclt and vcgt intrinsics respectively.
	* config/arm/arm_neon_builtins.def: Remove entry for
	vcgt and vcgtu.