Fix logic error in 32-bit trampolines.

Fix logic error in 32-bit trampolines.

The test in the PowerPC 32-bit trampoline support is backwards.  It aborts
if the trampoline size is greater than the expected size.  It should abort
when the trampoline size is less than the expected size.  I fixed the test
so the operands are reversed.  I then folded the load immediate into the
compare instruction.

I verified this by creating a 32-bit trampoline program and manually
changing the size of the trampoline to be 48 instead of 40.  The program
aborted with the larger size.  I updated this code and ran the test again
and it passed.

I added a test case that runs on PowerPC 32-bit Linux systems and it calls
the __trampoline_setup function with a larger buffer size than the
compiler uses.  The test is not run on 64-bit systems, since the function
__trampoline_setup is not called.  I also limited the test to just Linux
systems, in case trampolines are handled differently in other systems.

libgcc/
2021-04-23  Michael Meissner  <meissner@linux.ibm.com>

	PR target/98952
	* config/rs6000/tramp.S (__trampoline_setup, elfv1 #ifdef): Fix
	trampoline size comparison in 32-bit by reversing test and
	combining load immediate with compare.
	(__trampoline_setup, elfv2 #ifdef): Fix trampoline size comparison
	in 32-bit by reversing test and combining load immediate with
	compare.

gcc/testsuite/
2021-04-23  Michael Meissner  <meissner@linux.ibm.com>

	PR target/98952
	* gcc.target/powerpc/pr98952.c: New test.