Fix typo in adb commandline help

Android developers are not expected to have PDP-11s.
diff --git a/adb/commandline.c b/adb/commandline.c
index 7410dce..548d362 100644
--- a/adb/commandline.c
+++ b/adb/commandline.c
@@ -151,7 +151,7 @@
         "\n"
         "networking:\n"
         "  adb ppp <tty> [parameters]   - Run PPP over USB.\n"
-        " Note: you should not automatically start a PDP connection.\n"
+        " Note: you should not automatically start a PPP connection.\n"
         " <tty> refers to the tty for PPP stream. Eg. dev:/dev/omap_csmi_tty1\n"
         " [parameters] - Eg. defaultroute debug dump local notty usepeerdns\n"
         "\n"