usb: s3c-hsotg: Use devm_* functions in s3c-hsotg.c file

devm_* functions are used to replace kzalloc, request_mem_region, ioremap
and request_irq functions in probe call. With the usage of devm_* functions
explicit freeing and unmapping is not required.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>