testsuite: Fix up refactored scanltranstree.exp functions [PR116522]

testsuite: Fix up refactored scanltranstree.exp functions [PR116522]

When adding RTL variants of the scan-ltrans-tree* functions in:
r15-3254-g3f51f0dc88ec21c1ec79df694200f10ef85915f4
I messed up the name of the underlying scan function to invoke.  The
code currently attempts to invoke functions named
scan{,-not,-dem,-dem-not} but should instead be invoking
scan-dump{,-not,-dem,-dem-not}.  This patch fixes that.

gcc/testsuite/ChangeLog:

	PR testsuite/116522
	* lib/scanltranstree.exp: Fix name of underlying scan function
	used for scan-ltrans-{tree,rtl}-dump{,-not,-dem,-dem-not}.