PWM channels that are configured to support Variable Frequency Mode
generate a signal of fixed duty cycle (50%) and variable frequency. In
such cases, the desired frequency setting is calculated differently
internally, according to a new formula.
Change-Id: I5cbbab9fa75fdd22c75811e5f61e69b8f4abe020
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>