xtensa: Partially Revert "xtensa: Remove unnecessary of_platform_populate with default match table"

This partially reverts commit 69d99e6c keeping only the main
purpose of the original commit which is the removal of
of_platform_populate() call. The moving of of_clk_init() caused changes
in the initialization order breaking booting.

Fixes: 69d99e6c ("xtensa: Remove unnecessary of_platform_populate with default match table")
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Rob Herring <robh@kernel.org>