USB: Add missing word to comment in mod_devicetable.h

The documentation of match_flags in struct usb_device_id said:
'Bit mask controlling of the other fields are used to match against new devices.'
Changed to:
'Bit mask controlling which of the other fields are used to match against new devices.'
By adding the word 'which' and editing the next lines to not exceed 80 chars.

Signed-off-by: Sharon Dvir <sharon.dvir1@mail.huji.ac.il>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>