Added Board Varient STM32F103VB.
Replaced #ifdef STM32_HIGH_DENSITY
with #if STM32_NR_PORTS > 4
Where it makes sense for High Pin count medium density parts like the
STM32F103VB.
Added Board Varient STM32F103B.
Replaced #ifdef STM32_HIGH_DENSITY
with #if STM32_NR_PORTS > 4
Where it makes sense for High Pin count medium density parts like the
STM32F103VB.