[SystemZ] Don't use libcall for 128 bit shifts.

Expand 128 bit shifts instead of using a libcall.

This patch removes the 128 bit shift libcalls and thereby causes
ExpandShiftWithUnknownAmountBit() to be called.

Review: Ulrich Weigand

Differential Revision: https://reviews.llvm.org/D101993

(cherry picked from commit 1c4cb510)