middle-end/108086 - avoid unshare_expr when remapping SSA names

middle-end/108086 - avoid unshare_expr when remapping SSA names

r0-89280-g129a37fc319db8 added unsharing to remap_ssa_name but
that wasn't in the version of the patch posted.  That has some
non-trivial cost through mostly_copy_tree_r and copy_tree_r but
more importantly it doesn't seem to be necessary.  I've successfully
bootstrapped and tested with an assert we only get
tree_node_can_be_shared trees here.

Bootstrapped and tested on x86_64-unknown-linux-gnu with all
languages.

	PR middle-end/108086
	* tree-inline.cc (remap_ssa_name): Do not unshare the
	result from the decl_map.