fmt, parser: fix pos.last_line for assembly blocks (#10877)

vlib/v/fmt/tests/newlines_keep.vv

@@ -22,3 +22,11 @@ fn y_with_attr() {
 [typedef]
 struct FooWithAttr {
 }
+
+fn between_assembly_blocks() {
+	asm amd64 {
+	}
+
+	asm i386 {
+	}
+}

vlib/v/parser/parser.v

@@ -1067,7 +1067,7 @@ fn (mut p Parser) asm_stmt(is_top_level bool) ast.AsmStmt {
 		output: output
 		input: input
 		clobbered: clobbered
-		pos: pos.extend(p.tok.position())
+		pos: pos.extend(p.prev_tok.position())
 		is_basic: is_top_level || output.len + input.len + clobbered.len == 0
 		scope: scope
 		global_labels: global_labels