cmd/compile/internal/pgo: remove some unused fields
cmd/compile/internal/pgo: remove some unused fields

We intentionally don't use file path so it is resilient to code
moving. OrigName and Objfile are also not used currently. Remove
them. (We can add them back if it turns out to be useful.)

Change-Id: I7975d78c874bc21475b9119301088452a4426cb9
Reviewed-on: https://go-review.googlesource.com/c/go/+/447801
Reviewed-by: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>
Run-TryBot: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go