kernel code reading: pci init on pseries
kernel code reading: pseries iommu setup handle

On pseries platform, the iommu handle is initialized at the very begining.
userspace code test: ppc64 asm function call

This is an example extract from the gcc -S bar.c.

Some comments are added.
userspace code test: ppc64 asm optimization

There is no need to save/restore the save value on stack.
userspace code test: ppc64 asm optimize

Since we just have one parameter and do simple calculation.

Just use r3 as the oprand.