configs: Re-run migrations

As the CI test for stopping platforms from being merged that were
defining symbols that had Kconfig entries, a small number of symbols
needed to be migrated again.  Do so, and catch two cases the README
should also have been updated but was not.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/j721s2_evm_r5_defconfig b/configs/j721s2_evm_r5_defconfig
index 09f832e..996efd4 100644
--- a/configs/j721s2_evm_r5_defconfig
+++ b/configs/j721s2_evm_r5_defconfig
@@ -111,6 +111,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_BANKS_DETECT=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_SFDP_SUPPORT=y
 CONFIG_SPI_FLASH_SOFT_RESET=y