vect: Fix stray argument in call to dump_printf_loc

vect: Fix stray argument in call to dump_printf_loc

One call to dump_printf_loc had a stray left-over argument
from an earlier version of the patch.  This went unnoticed
on aarch64-linux-gnu and x86_64-linux-gnu since the parameters
that actually mattered were passed in FPRs rather than GPRs,
but I assume this is the reason for the i686-linux-gnu failures
that Jakub hit.

gcc/
	* tree-vect-slp.cc (vect_optimize_slp_pass::dump): Remove bogus
	argument.