That "else" was needed due to gc DCE limitations.
Now it's not the case and we can avoid go lint complaints.
(See #23521 and https://golang.org/cl/91056.)

There is inlining test for bigEndianWord, so if test
is passing, no performance regression should occur.

Change-Id: Id84d63f361e5e51a52293904ff042966c83c16e9
Reviewed-on: https://go-review.googlesource.com/104555Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>