usb: gadget: udc: s3c2410_udc.c: Remove some unused functions

Removes some functions that are not used anywhere:
s3c2410_udc_clear_ep_state() s3c2410_udc_set_ep0_sse_out()

This was partially found by using a static code analysis program called cppcheck.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Felipe Balbi <balbi@ti.com>