Add Book3s_64 offsets to asm-offsets.c

We need to access some VCPU fields from assembly code. In order to get
the proper offsets, we have to define them in asm-offsets.c.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>