pwmgen-v2.c: rename period to pwm_period to lessen confusion
pwmgen-v2.c: rename period to pwm_period to lessen confusion

make it clearly distinguishable from thread period

strahlex/machinekit,strahlex/machinekit,strahlex/machinekit,strahlex/machinekit,strahlex/machinekit,strahlex/machinekit,strahlex/machinekit