clk: imx: pll14xx: Use register defines consistently

The driver has defines for the registers, but they are mostly unused.
Use the defines consistently throughout the driver. While at it rename
DIV_CTL to DIV_CTL0 because that's the name in the reference manual.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Link: https://lore.kernel.org/r/20220304125256.2125023-2-s.hauer@pengutronix.de


Signed-off-by: Abel Vesa <abel.vesa@nxp.com>