gold: Update testsuite/split_[i386|x32|x86_64].sh

Update testsuite/split_i386.sh, testsuite/split_x32.sh and
testsuite/split_x86_64.sh for

commit f9ff65d4
Author: Alan Modra <amodra@gmail.com>
Date:   Thu Oct 8 10:27:43 2020 +1030

    [GOLD] Increase --split-stack-adjust-size

	* testsuite/split_i386.sh: Updated for --split-stack-adjust-size
	default change.
	* testsuite/split_x32.sh: Likewise.
	* testsuite/split_x86_64.sh: Likewise.