dt-bindings: dma: dw-axi-dmac: extend the number of interrupts

The Canaan k210 apparently has a Sysnopsys Designware AXI DMA
controller, but according to the documentation & devicetree it has 6
interrupts rather than the standard one. Support the 6 interrupt
configuration by unconditionally extending the binding to a maximum of
8 per-channel interrupts thereby matching the number of possible
channels.

Link: https://canaan-creative.com/wp-content/uploads/2020/03/kendryte_standalone_programming_guide_20190311144158_en.pdf #Page 51
Reviewed-by: Serge Semin <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/dma/snps,dw-axi-dmac.yaml

···
       - const: axidma_apb_regs
 
   interrupts:
-    maxItems: 1
+    description:
+      If the IP-core synthesis parameter DMAX_INTR_IO_TYPE is set to 1, this
+      will be per-channel interrupts. Otherwise, this is a single combined IRQ
+      for all channels.
+    minItems: 1
+    maxItems: 8
 
   clocks:
     items: