usb: gadget: remove u32 castings of address passed to readl()

Removes a couple of:
|drivers/usb/gadget/s3c-hsudc.c: In function 's3c_hsudc_epin_intr':
|drivers/usb/gadget/s3c-hsudc.c:438:2: warning: passing argument 1 of '__raw_readl' makes pointer from integer without a cast
|arch/arm/include/asm/io.h:104:19: note: expected 'const volatile void *' but argument is of type 'unsigned int'

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>