UPSTREAM: mac80211-hwsim: remove unnecessary hwname check

The hwname will always be set if idx is negative (as it's
a u32 read into an s64 it can't overflow either) so we can
remove the unnecessary check for hwname being non-NULL.

This was reported by smatch.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry picked from commit 6b67e01f)
Bug: 70214720
Change-Id: I02fb34c32ec070a566ae4bd230bdb229a01b3f78
Signed-off-by: Alistair Strachan <astrachan@google.com>