reflect: correct documentation of Value.UnsafeAddr

The doc mentions that "UnsafeAddr returns a _pointer_ to v's data", but
it returns a uintptr instead, which don't have pointer semantic.

Change-Id: I557d5597cbc485356ca803eb496a99d6db8c63ba
Reviewed-on: https://go-review.googlesource.com/c/go/+/350690
Trust: Cuong Manh Le <[email protected]>
Run-TryBot: Cuong Manh Le <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>

Author: cuonglm

src/reflect/value.go

@@ -2473,7 +2473,7 @@ func (v Value) Uint() uint64 {
 // which ensures cmd/compile can recognize unsafe.Pointer(v.UnsafeAddr())
 // and make an exception.
 
-// UnsafeAddr returns a pointer to v's data.
+// UnsafeAddr returns a pointer to v's data, as a uintptr.
 // It is for advanced clients that also import the "unsafe" package.
 // It panics if v is not addressable.
 func (v Value) UnsafeAddr() uintptr {