Fix test case label check

Several (but not all) of the labels that are checked for in this test case
are checked as strings instead of labels.  This can cause an apparent test
case failure if they are tested in an appropriately named directory.

For example, one of them that fails:

define zeroext i32 @test2(i32 %A.u, i32 %B.u)  {
; A8: test2
; A8: uxtab  r0, r0, r1


Output that causes it to fail:

. . .
	.file	"/home/seurer/llvm/llvm-test2/test/CodeGen/Thumb2/thumb2-uxt_rot.ll"
. . .
	.globl	test2
	.align	1
	.type	test2,%function
	.code	16                      @ @test2
	.thumb_func
test2:
	.fnstart


The "A8: test2" matches on the directory name instead of the label.

llvm-svn: 253702