CLEANUP: cfgparse: Remove duplication of `MAX_LINE_ARGS + 1`

We can calculate the number of possible arguments based off the size of the
`args` array. We should do so to prevent the two values from getting out of
sync.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index b1274cd..fa2072a 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1961,7 +1961,7 @@
 			uint32_t err;
 			char *errptr;
 
-			arg = MAX_LINE_ARGS + 1;
+			arg = sizeof(args) / sizeof(*args);
 			outlen = outlinesize;
 			err = parse_line(line, outline, &outlen, args, &arg,
 					 PARSE_OPT_ENV | PARSE_OPT_DQUOTE | PARSE_OPT_SQUOTE |