68daca9f28c5df384ae462cf, in the course of
fixing another bug, added a check that meant that a page fault due
to an instruction access would fail if the vma did not have the
VM_EXEC flag set.  This gives an inconsistent enforcement on these
CPUs of the no-execute status of the vma (since reading from the page
is sufficient to allow subsequent execution from it), and causes old
versions of ppc32 glibc (2.2 and earlier) to fail, since they rely
on executing the word before the GOT but don't have it marked
executable.

This fixes the problem by allowing execution from readable (or writable)
areas on CPUs which do not provide separate control over data and
instruction reads.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Jon Loeliger <jdl@freescale.com>
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