reduce codesize in bk1080 driver

[gartnl]

In the bk1080.c initialisation function there is a way to save 32 bytes. Since I don't know how to create a pull request for 1 file from a fork this is the save route, just a suggestion of the code:

	BK1080_SetFrequency(Frequency); // call the excisting function instead of directly writing to bk1080 registers
	//BK1080_WriteRegister(BK1080_REG_03_CHANNEL, Frequency - 760);
	//SYSTEM_DelayMs(10);
	//BK1080_WriteRegister(BK1080_REG_03_CHANNEL, (Frequency - 760) | 0x8000);