clk: zynqmp: fix check for fractional clock

The firmware sets BIT(13) in clkflag to mark a divider as fractional
divider. The clock driver copies the clkflag straight to the flags of
the common clock framework. In the common clk framework flags, BIT(13)
is defined as CLK_DUTY_CYCLE_PARENT.

Add a new field to the zynqmp_clk_divider to specify if a divider is a
fractional devider. Set this field based on the clkflag when registering
a divider.

At the same time, unset BIT(13) from clkflag when copying the flags to
the common clk framework flags.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>