xtensa: fix PR target/90922

xtensa: fix PR target/90922

Stack pointer adjustment code in prologue missed a case of no
callee-saved registers and a stack frame size bigger than 128 bytes.
Handle that case.

This fixes the following gcc tests with call0 ABI:
  gcc.c-torture/execute/stdarg-2.c
  gcc.dg/torture/pr55882.c
  gcc.dg/torture/pr57569.c

2019-06-18  Max Filippov  <jcmvbkbc@gmail.com>
gcc/
	* config/xtensa/xtensa.c (xtensa_expand_prologue): Add stack
	pointer adjustment for the case of no callee-saved registers and
	stack frame bigger than 128 bytes.

From-SVN: r272455