ARM: at91/tc: add device tree support to atmel_tclib

Device tree support added to atmel_tclib: the generic Timer Counter
library. This is used by the clocksource/clockevent driver tcb_clksrc.

The current DT enabled platforms are also modified to use it:
- .dtsi files are modified to add Timer Counter Block entries
- alias are created to allow identification of each block
- clkdev lookup tables are added for clocks identification.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>