updated for mbed os 5.4

Revision:
2:22ab4fcc5293
Parent:
1:cbcb7c2d43cd
--- a/mbed-os.lib	Fri Sep 20 15:10:15 2019 +0000
+++ b/mbed-os.lib	Fri Nov 08 10:31:30 2019 +0000
@@ -1,1 +1,1 @@
-https://github.com/ARMmbed/mbed-os/#1bf6b20df9d3cd5f29f001ffc6f0d0fcbbb96118
+https://github.com/ARMmbed/mbed-os/#3a57ec7401a77b8b98f6356a1498cb154229483f