Let's not hide the fact that these variables are structs/enums.
We are filling up the namespace badly enough, we should be prefixing as
much as we can with the module names at least. As users we already run
often enough in namespace colisions we don't have to make it worse.
* CLOCK_3V3_xxx enums renamed to RCC_CLOCK_3V3_xxx
* clock enums (PLL, HSI, HSE ...) prefixed with RCC_
* scale enum of pwr module prefixed with PWR_
d680be81b5