path solver: Solve PHI imports first for ranges.

PHIs must be resolved first while solving ranges in a block,
regardless of where they appear in the import bitmap.  We went through
a similar exercise for the relational code, but missed these.

Tested on x86-64 & ppc64le Linux.

gcc/ChangeLog:

	PR tree-optimization/103202
	* gimple-range-path.cc
	(path_range_query::compute_ranges_in_block): Solve PHI imports first.