In addition to looking for DT based parents, support clkdev based
clk_lookups. This should allow non-DT based clk drivers to participate
in the parent lookup process.

Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>