Fix riscv malloc error on small alignment after norvc.

Fix riscv malloc error on small alignment after norvc.

	gas/
	* config/tc-riscv.c (riscv_frag_align_code): New local insn_alignment.
	Early return if bytes less than or equal to insn_alignment.
	* testsuite/gas/riscv/align-1.l: New.
	* testsuite/gas/riscv/align-1.s: New.
	* testsuite/gas/riscv/riscv.exp: Use run_dump_tests.  Use run_list_test
	for align-1.