Rename expand_powcabs pass to expand_pow

Rename expand_powcabs pass to expand_pow

Since cabs expansion was removed from this pass,
it would be good to rename it.

Bootstrapped and tested on x86_64-linux-gnu

gcc/ChangeLog:

	* passes.def (expand_pow): Renamed from expand_powcabs.
	* timevar.def (TV_TREE_POWCABS): Remove.
	(TV_TREE_POW): Add
	* tree-pass.h (make_pass_expand_powcabs): Rename to ...
	(make_pass_expand_pow): This.
	* tree-ssa-math-opts.cc (class pass_expand_powcabs): Rename to ...
	(class pass_expand_pow): This.
	(pass_expand_powcabs::execute): Rename to ...
	(pass_expand_pow::execute): This.
	(make_pass_expand_powcabs): Rename to ...
	(make_pass_expand_pow): This.

gcc/testsuite/ChangeLog:

	* gcc.dg/pow-sqrt-synth-1.c: Update testcase for renamed pass.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>