cmd/pprof: make ObjAddr a no-op

https://golang.org/cl/318049 replaced driver.ObjFile.Base with
driver.ObjFile.ObjAddr. We don't support shared libraries, so these
should be no-op, but CL 318049 accidentally failed to account from the
change in no-op behavior from returning 0 to passing through addr.

Fixes #46636

Change-Id: Iab82224c7db722a1e257ec6e305218e22114d0a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/325809


Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>