cmd/internal/obj: reorder ppc64 MOV* optab entries
cmd/internal/obj: reorder ppc64 MOV* optab entries

These are always sorted and grouped during initialization of the
actual opcode -> optab map generation. Thus, their initial location
in optab is mostly aimed at readability. This cleanup is intends to
ease reviewing of future patches which simplify, combine, or remove
MOV* optab entries.

Change-Id: I87583ed34fab79e0f625880f419d499939e2a9e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/300612
Reviewed-by: Lynn Boger <b27445fe6fb259c37b8e0a4ce56e22e2413754bf@linux.vnet.ibm.com>
Trust: Emmanuel Odeke <bd234ba4276433f0e5fc7a8fa2d18274fa711567@orijtech.com>

nawawi/go,cloudflare/go,golang/go,nawawi/go,golang/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,golang/go,CAFxX/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,cloudflare/go,CAFxX/go,cloudflare/go,CAFxX/go