Revert "[DebugInfo] Re-engineer a test to be stricter, add XFails"

This reverts commit e05c10380c.

See parent commit, there's a bot which isn't captured in the XFail list,
reverting til I work out what it is.

llvm/test/DebugInfo/Generic/missing-abstract-variable.ll

@@ -1,10 +1,5 @@
 ; RUN: %llc_dwarf -O0 -filetype=obj < %s | llvm-dwarfdump -v -debug-info - | FileCheck %s
 
-; The formal parameter 'b' for Function 'x' when inlined within 'a' is lost on
-; powerpc64 (and on x86_64 at at least -O2). Presumably this is a SelectionDAG
-; issue.
-; XFAIL: powerpc64
-
 ; Build from the following source with clang -O2.
 
 ; The important details are that 'x's abstract definition is first built during
@@ -83,7 +78,6 @@
 ; fastisel succeeds).
 ; CHECK:     DW_TAG_formal_parameter
 ; CHECK-NOT: DW_TAG
-; CHECK:       DW_AT_location
 ; CHECK:       DW_AT_abstract_origin {{.*}} "b"
 
 ; CHECK-NOT: {{DW_TAG|NULL}}