Fixes the following sparse warning:

drivers/usb/musb/musb_dsps.c:270:6: warning:
 symbol 'dsps_musb_clear_ep_rxintr' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>