reflect: simplify array value comparable check

reflect: simplify array value comparable check

If array element is not interface, array or struct, we just need to
check whether the array element type is comparable.

Change-Id: I1ab94cfa17ae86feb6cd3fbdf878af5a776e7bec
Reviewed-on: https://go-review.googlesource.com/c/go/+/426194
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>