A couple of filecheck patterns had not been hooked up with the patterns suffering from some drift. As this test is old and llvm-objdump has improved a lot, take this opportunity to hide the instruction encoding. I've also taken out a lot of the explanatory comments that llvm-objdump improvements make redundant, as these comments oftern don't get updated when addresses change.
Depends on D104701 for objdump improvements
It looks like the CHECK-PI-ARM-PLT block is not checked.