aarch64: Fix undefined code in vect_ctz_1.c

The testcase gcc.target/aarch64/vect_ctz_1.c fails execution when running
with -march=armv9-a due to the testcase calls __builtin_ctz with a value of 0.
The testcase should not depend on undefined behavior of __builtin_ctz. So this
changes it to use the g form with the 2nd argument of 32. Now the execution part
of the testcase work. It still has a scan-assembler failure which should be fixed
seperately.

Tested on aarch64-linux-gnu.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/vect_ctz_1.c (TEST): Use g form of the builtin and pass 32
	as the value expected at 0.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>