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/M53017EVB_defconfig b/configs/M53017EVB_defconfig
index 28d51ea..1032891 100644
--- a/configs/M53017EVB_defconfig
+++ b/configs/M53017EVB_defconfig
@@ -41,6 +41,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=137
 CONFIG_DM_ETH=y
 CONFIG_MCFFEC=y
 CONFIG_SYS_UNIFY_CACHE=y