Revert "clk: Detect failure to set defaults"

This reverts commit 92f1e9a4.
The aforementioned patch causes massive breakage on all platforms which
have 'assigned-clock' DT property in their DT which references any clock
that are not supported by the platform clock driver. That can easily
happen either in SPL, or because the clock driver is reduced. Currently
it seems all iMX8M are affected and fail to boot altogether.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Peng Fan <peng.fan@oss.nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>