at91: at91sam9261.c: fix typo in t2_clk alias for atmel_tcb.0

This was a typo in clockdev declaration for at91sam9261 SoC.
Fix the kernel hanging when switching clocksource to TC (tcb_clksrc).

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Remy Bohmer <linux@bohmer.net>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>