clk: vc5: Add bindings for IDT VersaClock 5P49V5923 and 5P49V5933

Add bindings for IDT VersaClock 5 5P49V5923 and 5P49V5933 chips.
These are I2C clock generators with optional clock source from
either XTal or dedicated clock generator and, depending on the
model, two or more clock outputs.

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: devicetree@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>