testsuite: Enable reduced parallel batch sizes

testsuite: Enable reduced parallel batch sizes

Various aarch64 tests attempt to reduce the batch size for parallel test
execution to a single test per batch, but it looks like the necessary
changes to gcc_parallel_test_run_p were accidentally omitted when the
aarch64-*-acle-asm.exp files were merged.  This patch corrects that
omission.

This does have a measurable performance impact when running a limited
number of tests.  For example, in aarch64-sve-acle-asm.exp the use of
torture options results in 16 compiler executions for each test; when
running two such tests I observed a total test duration of 3m39 without
this patch, and 1m55 with the patch.  A full batch of 10 tests would
have taken over 15 minutes to run on this machine.

gcc/testsuite/ChangeLog:

	* lib/gcc-defs.exp
	(gcc_runtest_parallelize_limit_minor): New global variable.
	(gcc_parallel_test_run_p): Use new variable for batch size.