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/octeon_ebb7304_defconfig b/configs/octeon_ebb7304_defconfig
index 71df8cd..cf251ab 100644
--- a/configs/octeon_ebb7304_defconfig
+++ b/configs/octeon_ebb7304_defconfig
@@ -56,6 +56,7 @@
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=256
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_ATMEL=y
 CONFIG_SPI_FLASH_SPANSION=y