clk: davinci: da850-pll: change PLL0 to CLK_OF_DECLARE

PLL0 on davinci/da850-type device needs to be registered early in boot
because it is needed for clocksource/clockevent. Change the driver
to use CLK_OF_DECLARE for this special case.

Reviewed-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>
Link: lkml.kernel.org/r/20180525181150.17873-8-david@lechnology.com