pwm: hibvt: Convert to devm_platform_ioremap_resource()

Use devm_platform_ioremap_resource() to simplify code. While at it, also
declare the "i" and "ret" variables on the same line since they are of
the same type.

Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>