[testsuite, nvptx] Borrow ia64-sync-*.c test-cases in gcc.target/nvptx

In absence of nvptx-enabling for effective target sync_int_long (see PR96494),
copy a few test-cases to gcc.target/nvptx.

Tested on nvptx.

gcc/testsuite/ChangeLog:

	* gcc.target/nvptx/ia64-sync-1.c: New test.
	* gcc.target/nvptx/ia64-sync-2.c: New test.
	* gcc.target/nvptx/ia64-sync-3.c: New test.
	* gcc.target/nvptx/ia64-sync-4.c: New test.