ping: fix help text to show what parameter -p takes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/ping.c b/networking/ping.c
index e70bb7e..506e7b1 100644
--- a/networking/ping.c
+++ b/networking/ping.c
@@ -104,7 +104,7 @@
 //usage:     "\n			(can exit earlier with -c CNT)"
 //usage:     "\n	-q		Quiet, only display output at start"
 //usage:     "\n			and when finished"
-//usage:     "\n	-p		Pattern to use for payload"
+//usage:     "\n	-p HEXBYTE	Pattern to use for payload"
 //usage:
 //usage:# define ping6_trivial_usage
 //usage:       "[OPTIONS] HOST"
@@ -115,7 +115,7 @@
 //usage:     "\n	-I IFACE/IP	Source interface or IP address"
 //usage:     "\n	-q		Quiet, only display output at start"
 //usage:     "\n			and when finished"
-//usage:     "\n	-p		Pattern to use for payload"
+//usage:     "\n	-p HEXBYTE	Pattern to use for payload"
 //usage:
 //usage:#endif
 //usage: