[gas] Emit v2 .debug_line for -gdwarf-2

[gas] Emit v2 .debug_line for -gdwarf-2

Currently, when using -gdwarf-2, gas emits a v3 .debug_line contribution.

Fix this by emitting a v2 .debug_line contribution instead.

gas/ChangeLog:

2023-01-31  Tom de Vries  <tdevries@suse.de>

	PR 23941
	* dwarf2dbg.c (DWARF2_LINE_VERSION): Set to 2 for -gdwarf-2.
	(DWARF2_LINE_OPCODE_BASE): Handle DWARF2_LINE_VERSION == 2.
	(dwarf2_directive_loc): Bump dwarf_level when encountering
	v3 .loc options.
	(out_debug_line): Don't output v3 standard opcodes for v2.
	* testsuite/gas/i386/debug1.d: Update.
	* testsuite/gas/i386/dwarf2-line-1.d: Update.
	* testsuite/gas/i386/dwarf2-line-4.d: Update.