Workaround PR68256 on AArch64

Workaround PR68256 on AArch64

> This is causing a bootstrap comparison failure in gcc/go/gogo.o.

I've had a look at this and the trigger is the
aarch64_use_constant_blocks_p change which appears to be causing a
bootstrap comparison failure because of differences to offsets when
built with debug and without debug. I don't think the problem is
specifically in the backend but this needs some careful
investigation. For now, in the interest of go bootstraps continuing on
trunk - I'm proposing a patch that partially rolls back the change in
aarch64_use_constant_blocks_p and am still looking into the issue but
it will take me some more time to get to the bottom of the issue.

Bootstrapped on aarch64-none-linux-gnu including (c,c++ and go) -
testing finished ok.

2015-11-10  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>

	PR bootstrap/68256
	* config/aarch64/aarch64.c (aarch64_use_constant_blocks_p):
	Return false.

From-SVN: r230085