RCC Exported Functions

Modules
	HSE
	HSI
	LSE
	LSI
	MSI
	LSCO
	System
	MCO
	Peripheral Clock Source
	RTC
	PLL
	PLLSAI1
	PLLSAI2
	FLAG Management
	IT Management
	De-initialization function
	Get system and peripherals clocks frequency functions
	Return the frequencies of different on chip clocks; System, AHB, APB1 and APB2 buses clocks and different peripheral clocks available on the device.