selftests/powerpc: exec() with suspended transaction

Perform an exec() class syscall with a suspended transaction.

This is a test for the bug we fixed in 8e96a87c

 ("powerpc/tm: Always
reclaim in start_thread() for exec() class syscalls").

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
[mpe: Fix build errors, use a single binary for the test]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>