rs6000: Fix typo on vec_vsubcuq in rs6000-overload.def [PR108396]

rs6000: Fix typo on vec_vsubcuq in rs6000-overload.def [PR108396]

As Andrew pointed out in PR108396, there is one typo in
rs6000-overload.def on built-in function vec_vsubcuq:

  [VEC_VSUBCUQ, vec_vsubcuqP, __builtin_vec_vsubcuq]

"vec_vsubcuqP" should be "vec_vsubcuq", this typo caused
us to define vec_vsubcuqP in rs6000-vecdefines.h instead
of vec_vsubcuq, so that compiler is not able to realize
the built-in function name vec_vsubcuq any more.

Co-authored-By: Andrew Pinski <apinski@marvell.com>
	PR target/108396

gcc/ChangeLog:

	* config/rs6000/rs6000-overload.def (VEC_VSUBCUQ): Fix typo
	vec_vsubcuqP with vec_vsubcuq.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr108396.c: New test.