dt: bindings: brcmnand: Add support for flash-edu

Adding support for EBI DMA unit (EDU).

Signed-off-by: Kamal Dasu <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Miquel Raynal <[e-mail]>
Link: https://lore.kernel.org/linux-mtd/[e-mail]

Documentation/devicetree/bindings/mtd/brcm,brcmnand.txt

···
                      (optional) NAND flash cache range (if at non-standard offset)
 - reg-names        : a list of the names corresponding to the previous register
                      ranges. Should contain "nand" and (optionally)
-                     "flash-dma" and/or "nand-cache".
-- interrupts       : The NAND CTLRDY interrupt and (if Flash DMA is available)
-                     FLASH_DMA_DONE
-- interrupt-names  : May be "nand_ctlrdy" or "flash_dma_done", if broken out as
-                     individual interrupts.
+                     "flash-dma" or "flash-edu" and/or "nand-cache".
+- interrupts       : The NAND CTLRDY interrupt, (if Flash DMA is available)
+                     FLASH_DMA_DONE and if EDU is avaialble and used FLASH_EDU_DONE
+- interrupt-names  : May be "nand_ctlrdy" or "flash_dma_done" or "flash_edu_done",
+                     if broken out as individual interrupts.
                      May be "nand", if the SoC has the individual NAND
                      interrupts multiplexed behind another custom piece of
                      hardware