usb: storage: sddr55: fix sparse warning

Fix the following sparse warning:

| drivers/usb/storage/sddr55.c:51:22: warning: symbol
|	'sddr55_usb_ids' was not declared. Should it
|	be static?

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>