Create a stack frame on ARM when

Create a stack frame on ARM when

- Function uses all scratch registers AND
- Function does not use any callee saved registers AND
- Stack size is too big to address with immediate offsets.

In this case a register must be scavenged to calculate the address of a stack
object, and the scavenger needs a spare register or emergency spill slot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97071 91177308-0d34-0410-b5e6-96231b3b80d8