ARM: at91: move SoC specific definitions to SoC folder

Move linux/atmel_tc.h to the SoC specific folder include/soc/at91.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>