https://golang.org/cl/246763 accidentally changed this from upper + 0 +
carry to upper + old vdsoSP + carry.
The old value of vdsoPC is usually zero, so this typically works.
However, the reentrant case will have a non-zero value, resulting in a
bogus returned time.
Fixes #49481
Change-Id: I0110b84277bf911804cb0ff8097aebf1b7eb100a
Reviewed-on: https://go-review.googlesource.com/c/go/+/362674
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>