tree-optimization/122647 - missing bool pattern for bool -> float conversion

tree-optimization/122647 - missing bool pattern for bool -> float conversion

The following adds missing support for bool to float conversion which
can be exposed via C++ __builtin_bit_cast.  It also corrects a too
lose check in vectorizable_conversion which would have resolved the
ICE but left us with the missed optimization.

	PR tree-optimization/122647
	* tree-vect-stmts.cc (vectorizable_conversion): Fix guard on
	bool to non-bool conversion.
	* tree-vect-patterns.cc (vect_recog_bool_pattern): Also handle
	FLOAT_EXPR from bool.

	* g++.dg/vect/pr122647.cc: New testcase.