* configure.ac: Add --enable-fix-cortex-a53-835769 option.
	* configure: Regenerate.
	* config/aarch64/aarch64.c (aarch64_override_options): Handle
	TARGET_FIX_ERR_A53_835769_DEFAULT.
	* config/aarch64/aarch64.opt (mfix-cortex-a53-835769): Set Init
	value to 2.
	* doc/install.texi (aarch64*-*-*): Document 
	new --enable-fix-cortex-a53-835769 option.

From-SVN: r216076