Update usage in README

Author: qzed

README.md

@@ -15,7 +15,7 @@ FLAGS:
     -V, --version    Prints version information
 
 SUBCOMMANDS:
-    dgpu           Control or query the dGPU power state
+    dgpu           Control or query the dGPU power state on the Surface Book 2
     help           Prints this message or the help of the given subcommand(s)
     latch          Control the latch/dtx-system on the Surface Book 2
     performance    Control or query the current performance-mode