staging: unisys: fix sig_read_data and sig_read_data functions

The sig_read_data() and sig_write_data() functions are involved in 2 steps
of calls.  They really don't need to be and this makes for much simpler
code.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>