Add specializations of addrmode2 that allow differentiating those forms

Add specializations of addrmode2 that allow differentiating those forms
which require the use of the shifter-operand. This will be used to split
the ldr/str instructions such that those versions needing the shifter operand
can get a different scheduling itenerary, as in some cases, the use of the
shifter can cause different scheduling than the simpler forms.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115066 91177308-0d34-0410-b5e6-96231b3b80d8