usb: gadget: s3c-hsotg: fix maxpacket size

This patch changes ep maxpacket value from 512 to 1024, because it's needed
to handle interupt and isochronous endpoints in high-speed mode. This change
doesn't affect on driver functioning, because fifo size (3072) is still enough
for the maximum transaction payload (3*1024 for high-speed high-bandwidtch
endpoints).

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>