Fix percentile_list option

Commit 802ad4a8 broke the parsing of the percentile list,
by neglecting to change the parser type fo a fio_fp64_t.

Also get rid of the def_percentile_list, just set the
default percentile list as the option default.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/options.c b/options.c
index 799e77a..4522fe4 100644
--- a/options.c
+++ b/options.c
@@ -2434,8 +2434,8 @@
 		.name	= "percentile_list",
 		.type	= FIO_OPT_FLOAT_LIST,
 		.off1	= td_var_offset(percentile_list),
-		.off2   = td_var_offset(overwrite_plist),
 		.help	= "Specify a custom list of percentiles to report",
+		.def    = "1:5:10:20:30:40:50:60:70:80:90:95:99:99.5:99.9:99.95:99.99",
 		.maxlen	= FIO_IO_U_LIST_MAX_LEN,
 		.minfp	= 0.0,
 		.maxfp	= 100.0,