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/sama5d3xek_nandflash_defconfig b/configs/sama5d3xek_nandflash_defconfig
index 7725115..f29a1b7 100644
--- a/configs/sama5d3xek_nandflash_defconfig
+++ b/configs/sama5d3xek_nandflash_defconfig
@@ -82,6 +82,7 @@
 CONFIG_FLASH_CFI_DRIVER=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=131
 CONFIG_NAND_ATMEL=y
 CONFIG_PMECC_CAP=4
 CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER=y