Refine the ARM EHABI test cases.

Since we have ARM unwind directive parser and assembler, we
can check the correctness in two stages:

1. From LLVM assembly (.ll) to ARM assembly (.s)
2. From ARM assembly (.s) to ELF object file (.o)

We already have several "*.s to *.o" test cases.  This CL adds
some "*.ll to *.s" test cases and removes the redundant "*.ll to *.o"
test cases.

New test cases to check "*.ll to *.s" code generator:

- ehabi.ll: Check the correctness of the generated unwind directives.
- section-name.ll: Check the section name of functions.

Removed test cases:

- ehabi-mc-cantunwind.ll
  (Covered by ehabi-cantunwind.ll, and eh-directive-cantunwind.s)
- ehabi-mc-compact-pr0.ll
  (Covered by ehabi.ll, eh-compact-pr0.s, eh-directive-save.s, and
   eh-directive-setfp.s)
- ehabi-mc-compact-pr1.ll
  (Covered by ehabi.ll, eh-compact-pr1.s, eh-directive-save.s, and
   eh-directive-setfp.s)
- ehabi-mc.ll
  (Covered by ehabi.ll, and eh-directive-integrated-test.s)
- ehabi-mc-section-group.ll
  (Covered by section-name.ll, and eh-directive-section-comdat.s)
- ehabi-mc-section.ll
  (Covered by section-name.ll, and eh-directive-section.s)
- ehabi-mc-sh_link.ll
  (Covered by eh-directive-text-section.s, and eh-directive-section.s)