[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

llvm-svn: 336286