When not compiling bootloader, a spinlock will be used for reading or writing
I2C internal devices/registers.
When compiling for bootloader, no need to use any lock.
No longer necessary to keep all reserved addresses in 'soc'.
Means 'soc' does not need to know about 'bt', for example.
Also means that Bluetooth can be enabled in config without any memory being reserved for BT
controller. Only if code calling the BT controller is linked in, will this memory be reserved...
