powerpc64/pseries: Define new hcalls

Summary:
Define new hcalls as in 'Linux on Power Architecture Platform Reference'
version 1.1 (24 March 2016) downloaded from:

https://members.openpowerfoundation.org/document/dl/469

Submitted by: Breno Leitao
Differential Revision: https://reviews.freebsd.org/D14281