[PATCH, LD, AArch64] Fix ifunc testisms

[PATCH, LD, AArch64] Fix ifunc testisms

This patch fixes some ifunc testisms after H.J. Lu's patch to enable the
use of IFUNC pointers in position dependent code for binutils. See PR
LD/23169 in binutils bugzilla.

The aarch64 ifunc error message test was changed to no longer expect
this error message as this is now an accepted combination. This patch
also disables the executable tests added by H.J. Lu for aarch64, just as
Alan Modra did with his patch, as these tests only seem to work on some
architectures.

ld/ChangeLog:
2018-07-19  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* testsuite/ld-aarch64/ifunc-9.d: Remove no longer expected error.
	* testsuite/ld-ifunc/ifunc.exp: Disable tests for aarch64.