mediatek: mt7623: replace kconfig symbol for snand driver

this change was missing during the spi-nand driver replacement, causing
build failure.

Signed-off-by: Chuanhong Guo <[email protected]>

target/linux/mediatek/mt7623/config-5.10

@@ -416,6 +416,7 @@ CONFIG_MTK_MMSYS=y
 CONFIG_MTK_PMIC_WRAP=y
 CONFIG_MTK_SCPSYS=y
 CONFIG_MTK_SMI=y
+# CONFIG_MTK_SPI_NAND is not set
 CONFIG_MTK_THERMAL=y
 CONFIG_MTK_TIMER=y
 # CONFIG_MTK_UART_APDMA is not set
@@ -550,7 +551,6 @@ CONFIG_SPI_MASTER=y
 CONFIG_SPI_MEM=y
 CONFIG_SPI_MT65XX=y
 # CONFIG_SPI_MTK_NOR is not set
-# CONFIG_SPI_MTK_SNFI is not set
 CONFIG_SPMI=y
 # CONFIG_SPMI_HISI3670 is not set
 CONFIG_SRCU=y