Do not enable -mblock-ops-vector-pair.

Testing has shown that using the load vector pair and store vector pair
instructions for block moves has some performance issues on power10.

A patch on June 11th modified the code so that GCC would not set
-mblock-ops-vector-pair by default if we are tuning for power10, but it would
set the option if we were tuning for a different machine and have load and store
vector pair instructions enabled.

This patch eliminates the code setting -mblock-ops-vector-pair.  If you want to
generate load vector pair and store vector pair instructions for block moves,
you must use -mblock-ops-vector-pair.

2022-08-03   Michael Meissner  <meissner@linux.ibm.com>

gcc/

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