ARM: dts: at91: sama5d2: add u-boot, dm-pre-reloc property for TCB

In order to use the TCB early in boot and in the SPL, add
u-boot,dm-pre-reloc property for the TCB and the clock that is used by
the driver (tcb0_clk).

Signed-off-by: Clément Léger <clement.leger@bootlin.com>