Convert CONFIG_SYS_MAX_FLASH_SECT to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MAX_FLASH_SECT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/qemu_arm64_defconfig b/configs/qemu_arm64_defconfig
index f7c93ba..8d7bc19 100644
--- a/configs/qemu_arm64_defconfig
+++ b/configs/qemu_arm64_defconfig
@@ -50,6 +50,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=256
 CONFIG_SYS_MAX_FLASH_BANKS=2
 CONFIG_SYS_MAX_FLASH_BANKS_DETECT=y
 CONFIG_DM_ETH=y