pwm: Fix dependencies on HAS_IOMEM

Drivers making use of IO remapping must depend on HAS_IOMEM.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>