マイナスの値が出ないように修正

Dependencies:   mbed HMC5883L_2

Revision:
0:26409a44f1f3
Child:
1:c91577293e84
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/HMC5883L.lib	Wed Feb 06 11:54:51 2019 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/teams/1519026547/code/HMC5883L/#ea1b30a71280