riscv: dts: canaan: fix the k210's timer nodes

riscv: dts: canaan: fix the k210's timer nodes

The timers on the k210 have non standard interrupt configurations,
which leads to dtbs_check warnings:

k210_generic.dtb: timer@502d0000: interrupts: [[14], [15]] is too long
From schema: Documentation/devicetree/bindings/timer/snps,dw-apb-timer.yaml

Split the timer nodes in two, so that the second timer in the IP block
can actually be accessed & in the process solve the dtbs_check warning.

Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220705215213.1802496-7-mail@conchuod.ie
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>