GE Attenuator / Mbed 2 deprecated VAM_DAX_RELIABILITY

update hcsr04.cpp by changing 20000 to 2000

Dependencies:   Stepper mbed SDFileSystem Ultrasonic PinDetect millis

Diff: SDFileSystem.lib

Revision:
7:ede305192e3b
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/SDFileSystem.lib	Thu Jan 10 01:32:38 2019 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/SDFileSystem/#8db0d3b02cec