USB: ssu100: add register parameter to ssu100_setregister

The function ssu100_setregister was hard coded to only set the MCR
register.  Add a register parameter so that other registers can be
set.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>