Remove unbalanced RPM put at driver unbind which resulted in a negative
usage count.

Fixes: 19891b20 ("pwm: pwm-tiehrpwm: PWM driver support for EHRPWM")
Signed-off-by: NJohan Hovold <johan@kernel.org>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>