[PowerPC] Update InputOps of Power10 SchedModel

Count of input operands affect pipeline forwarding in scheduling model.
Previous Power10 model definition arranges some instructions into
incorrect groups, by counting the wrong number of input operands.

This patch updates the model, setting the input operands count correctly
by excluding irrelevant immediate operands and count memory operands of
load instructions correctly.

Reviewed By: shchenz

Differential Revision: https://reviews.llvm.org/D153842