mmc: omap_hsmmc: use devm_request_irq

With devm_request_irq conversion free_irq can be removed in clean up path

Signed-off-by: Balaji T K <balajitk@ti.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>