arm: testsuite: skip mtp tests on thumb1

arm: testsuite: skip mtp tests on thumb1

These tests need access to the MRC instruction, but that isn't part of
of the Thumb1 ISA.  So skip the tests when this isn't the case.

gcc/testsuite/ChangeLog:

	* gcc.target/arm/mtp_1.c: Require arm32.
	* gcc.target/arm/mtp_2.c: Likewise.
	* gcc.target/arm/mtp_3.c: Likewise.
	* gcc.target/arm/mtp_4.c: Likewise.