Configure the Clock CLK_RTC

To configure the CLK_RTC, follow these steps:

1. 1.Configure the desired oscillator to operate as required, in the Clock Controller (CLKCTRL) peripheral.
2. 2.Write the Clock Select (CLKSEL) bit field in the Clock Selection (RTC.CLKSEL) register accordingly.

The CLK_RTC clock configuration is used by both RTC and PIT functionalities.