Remove setting -mblock-ops-vector-pair on power10.

Remove setting -mblock-ops-vector-pair on power10.

Testing has shown that using the load vector pair and store vector pair
instructions for block moves has some performance issues on power10.  This
patch does not set this option by default.  If it is a win in other
machines, this flag can be set in the ISA options.

2022-07-18   Michael Meissner  <meissner@linux.ibm.com>

gcc/

	* config/rs6000/rs6000.cc (rs6000_option_override_internal):
	Remove code setting -mblock-ops-vector-pair by default on
	power10.