cmd/compile: remove statement marks from secondary calls

Calls are code-generated in an alternate path that inherits
its positions from values, not from *SSAGenState.  The
default position on *SSAGenState was marked as not-a-statement,
but this was not applied to the value itself, leading to
spurious "is statement" marks in the output (convention:
after code generation in the compiler, everything is either
definitely a statement or definitely not a statement, nothing
is in the undetermined state).

This CL causes a 35 statement regression in ssa/stmtlines_test.
This is down from the earlier 150 because of all the other
CLs preceding this one that deal with the root causes of the
missing lines (repeated lines on nested calls hid missing lines).

This also removes some line repeats from ssa/debug_test.

Change-Id: Ie9a507bd5447e906b35bbd098e3295211df2ae01
Reviewed-on: https://go-review.googlesource.com/c/go/+/188018


Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>