spi: airoha: reduce the number of modification of REG_SPI_NFI_CNFG and REG_SPI_NFI_SE...

spi: airoha: reduce the number of modification of REG_SPI_NFI_CNFG and REG_SPI_NFI_SECCUS_SIZE registers

This just reduce the number of modification of REG_SPI_NFI_CNFG and
REG_SPI_NFI_SECCUS_SIZE registers during dirmap operation.

This patch is a necessary step to avoid reading flash page settings
from SNFI registers during driver startup.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patch.msgid.link/20251012121707.2296160-11-mikhail.kshevetskiy@iopsys.eu
Signed-off-by: Mark Brown <broonie@kernel.org>