Don't schedule LDRD on ARM

The load scheduler does not handle LDRD correctly right now, but it does
not prevent A_LDR with PF_D set from beeing scheduled.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@26637 3ad0048d-3df7-0310-abae-a5850022a9f2