cmd/internal/obj: remove param element from ppc64 optab
cmd/internal/obj: remove param element from ppc64 optab

This is rarely used, and is implied based on the
memory type of the operand.  This is a step towards
simplifying the MOV* pseudo opcodes on ppc64.

Similarly, remove the bogus param value from AVMULESB.

Change-Id: Ibad4d045ec6d8c5163a468b2db1dfb762ef674ee
Reviewed-on: https://go-review.googlesource.com/c/go/+/300177
Run-TryBot: Paul Murphy <2e1d8d6f81223fe22f04c5349bc2b02555a275af@ibm.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Lynn Boger <b27445fe6fb259c37b8e0a4ce56e22e2413754bf@linux.vnet.ibm.com>
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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