misc: ep93xx_pwm: use module_platform_driver_probe()

This patch uses module_platform_driver_probe() macro which makes
the code smaller and simpler.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>