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/at91sam9263ek_norflash_defconfig b/configs/at91sam9263ek_norflash_defconfig
index 2c354f3..c33fedb 100644
--- a/configs/at91sam9263ek_norflash_defconfig
+++ b/configs/at91sam9263ek_norflash_defconfig
@@ -52,6 +52,7 @@
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_FLASH_CFI_DRIVER=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=256
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_ATMEL=y
 CONFIG_DM_SPI_FLASH=y