[rcore][drm] GetTouchPointCount() returns 1 when screen is not touched

[larry104]

Just did a git pull to get the latest; compiled on a RaspberryPi 3 with make PLATFORM=PLATFORM_DRM

To reproduce just add to the core_input_multitouch.c a statement to print tCount and compile and run it.

When touching the screen first with your index finger when with your thumb and then releasing the index finger and after that the thumb the tCount will still show 1 even though nothing touches the screen anymore.