torture: Remove unused definition

The torture_parm() macro is the same as torture_param(), and torture_parm()
is not used.  This commit therefore removes torture_parm().

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>