USB: fix build bug in USB_ISIGHTFW

-tip tree testing found this build bug:

  drivers/built-in.o: In function `isight_firmware_load':
  isight_firmware.c:(.text+0x1ade08): undefined reference to `request_firmware'
  isight_firmware.c:(.text+0x1adf9c): undefined reference to `release_firmware'

select FW_LOADER in USB_ISIGHTFW.


From: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>