spi: airoha: add support of en7523 SoC (for 6.19)

Merge series from Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>:

Airoha EN7523 snfi controller almost identical to AN7581 one, so the same
driver can be used. The only known difference appears in the very specific
boot conditions, when attached serial console force EN7523 SoC boots
in undocumented (reserved) mode. In this mode dma reading of the flash
works incorrectly.

This patch series:
 * add support of EN7523 SoC
 * add spinand node to en7523 dts (so spinand flash finally becomes usable)
 * updates dt-bindings to mark driver as compatible with en7523
 * disable dma usage to prevent possible data damage if booting in
   reserved mode was detected.