arm64: dts: ti: k3-am62a7-sk: Describe the SPI NAND

arm64: dts: ti: k3-am62a7-sk: Describe the SPI NAND

Describe the octal SPI NAND available on the low-power starter kit.

The pinctrl configuration comes from TI fork.

With the current mainline tree, we currently get the following
performances:

eraseblock write speed is 7507 KiB/s
eraseblock read speed is 15802 KiB/s
page write speed is 7551 KiB/s
page read speed is 15609 KiB/s
2 page write speed is 7551 KiB/s
2 page read speed is 15609 KiB/s
erase speed is 284444 KiB/s
2x multi-block erase speed is 512000 KiB/s

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20250613182356.1272642-1-miquel.raynal@bootlin.com
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>