leds: Remove leds-renesas-tpu driver

The driver is superseded by the generic pwm-renesas-tpu driver used with
leds-pwm.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Bryan Wu <cooloney@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>