[ARM] [Assembler] Support negative immediates: cover few missing cases

Support for negative immediates was implemented in
https://reviews.llvm.org/rL298380, however few instruction options were missing.

This change adds negative immediates support and respective tests
for the following:

ADD
ADDS
ADDS.W
AND.W
ANDS
BIC.W
BICS
BICS.W
SUB
SUBS
SUBS.W

Differential Revision: https://reviews.llvm.org/D48649

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336286 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed