ARM: at91: sama5d3: get rid of atmel_tsadcc driver

Touchscreen support for at91_adc has been introduced so we can get rid of
atmel_tsadcc.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>