[ARM GlobalISel] Allow simple binary ops in Thumb2

Mark G_ADD, G_SUB, G_MUL, G_AND, G_OR and G_XOR as legal for both ARM
and Thumb2.

Extract the legalizer tests for these opcodes into another file.

Add tests for the instruction selector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349142 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed