clk: lpc32xx: add common clock framework driver

Add support for all configurable clocks found on NXP LPC32xx SoC.

The list contains several heterogenous groups of clocks:
* system clocks including multiple dividers and muxes,
* x397 PLL, HCLK PLL and USB PLL,
* peripheral clocks inherited from rtc, hclk and pclk,
* USB controller clocks: AHB slave, I2C, OTG, OHCI and device.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Michael Turquette <mturquette@baylibre.com>