Add a compatible string for the Elan eKTH5015M touch controller.

Judging from the current binding and commit bd3cba00 ("HID: i2c-hid:
elan: Add support for Elan eKTH6915 i2c-hid touchscreens"), eKTH5015M
appears to be compatible with eKTH6915. Notably the power-on sequence is
the same.

While at it, drop a redundant label from the example.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20240507144821.12275-3-johan+linaro@kernel.orgSigned-off-by: Benjamin Tissoires <bentiss@kernel.org>