[HELPERS] Added a BT_CalculateClockDivider API, supports 2 stage divider calculation currently.

The idea is to prevent drivers having to re-implement this boring calculation repeatedly.
[MACH] LM3Sxx - first implementation of Stellaris LM3Sxx series
[ARCH] ARM - systick reload value decremented by one
[HAL] LPCxx - bugix with Kconfig CAN device selection
[BSP] LM3Sxx - created BSP for LM3S9B92