The MOVFL instruction (which external PPC64 docs call mtcrf) can take
either a CR register or a constant. It doesn't make sense to specify
both, as the CR register implies the constant value. Specifying either
a register or a constant is enforced by the implementation in the
asmout method (case 69).

However, the optab was providing a form that specified both a constant
and a CR register, and was not providing a form that specified only a
constant. This CL fixes the optab table to provide a form that takes
only a constant.

No test because I don't know where to write it. The next CL in this
series will use the new instruction format.

Change-Id: I8bb5d3ed60f483b54c341ce613931e126f7d7be6
Reviewed-on: https://go-review.googlesource.com/44732
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>