ARM parsing and encoding of SBFX and UBFX.

ARM parsing and encoding of SBFX and UBFX.

Encode the width operand as it encodes in the instruction, which simplifies
the disassembler and the encoder, by using the imm1_32 operand def. Add a
diagnostic for the context-sensitive constraint that the width must be in
the range [1,32-lsb].

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136264 91177308-0d34-0410-b5e6-96231b3b80d8