[nvptx, testsuite] Add gcc.target/nvptx/sm*.c

[nvptx, testsuite] Add gcc.target/nvptx/sm*.c

Add a few test-cases that test passing each -misa=sm_xx version and verify that
the proper __PTX_SM__ is defined.

Tested on nvptx.

gcc/testsuite/ChangeLog:

2022-02-25  Tom de Vries  <tdevries@suse.de>

	* gcc.target/nvptx/sm30.c: New test.
	* gcc.target/nvptx/sm35.c: New test.
	* gcc.target/nvptx/sm53.c: New test.
	* gcc.target/nvptx/sm70.c: New test.
	* gcc.target/nvptx/sm75.c: New test.
	* gcc.target/nvptx/sm80.c: New test.