Move methods from TouchCursorInputMapperCommon.h into a cpp file

These methods are currently all used by two other files, but I want to
use one of them in TouchpadInputMapper.cpp. This means that I get
compilation errors saying the others are unused. Moving the method
definitions into a cpp file fixes this.

Bug: b/251196347
Test: builds without errors
Change-Id: Idc8b7bf2c8a1cb202e3122bcf5ff8552abbc9ca5
diff --git a/services/inputflinger/reader/Android.bp b/services/inputflinger/reader/Android.bp
index c93443a..a34cb4c 100644
--- a/services/inputflinger/reader/Android.bp
+++ b/services/inputflinger/reader/Android.bp
@@ -50,6 +50,7 @@
         "mapper/SensorInputMapper.cpp",
         "mapper/SingleTouchInputMapper.cpp",
         "mapper/SwitchInputMapper.cpp",
+        "mapper/TouchCursorInputMapperCommon.cpp",
         "mapper/TouchInputMapper.cpp",
         "mapper/TouchpadInputMapper.cpp",
         "mapper/VibratorInputMapper.cpp",