spi: airoha: return an error for continuous mode dirmap creation cases

spi: airoha: return an error for continuous mode dirmap creation cases

This driver can accelerate single page operations only, thus
continuous reading mode should not be used.

Continuous reading will use sizes up to the size of one erase block.
This size is much larger than the size of single flash page. Use this
difference to identify continuous reading and return an error.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Fixes: a403997c12019 ("spi: airoha: add SPI-NAND Flash controller driver")
Link: https://patch.msgid.link/20251012121707.2296160-2-mikhail.kshevetskiy@iopsys.eu
Signed-off-by: Mark Brown <broonie@kernel.org>