testsuite: arm: Use effective-target for pacbti-m-predef* tests

Update test cases to use -mcpu=unset/-march=unset feature introduced in
r15-3606-g7d6c6a0d15c.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/acle/pacbti-m-predef-1.c: Use effective-target
	arm_arch_v8_1m_main.
	* gcc.target/arm/acle/pacbti-m-predef-2.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-3.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-4.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-5.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-6.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-8.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-9.c: Likewise.
	* gcc.target/arm/acle/pacbti-m-predef-10.c: Likewise.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>