cmd/link: support PPC64 prefixed relocations for power10
Handle emitting (to ld) or resolving commonly used ELFv2 1.5
relocations. The new ISA provides PC relative addressing with
34 bit signed addresses, and many other relocations which can
replace addis + d-form type relocations with a single prefixed
instruction.
Updates #44549
Change-Id: I7d4f4314d1082daa3938f4353826739be35b0e81
Reviewed-on: https://go-review.googlesource.com/c/go/+/355149 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Paul Murphy <murp@ibm.com>