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/boston64r2_defconfig b/configs/boston64r2_defconfig
index 4a41e6b..e5c3706 100644
--- a/configs/boston64r2_defconfig
+++ b/configs/boston64r2_defconfig
@@ -46,6 +46,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=1024
 CONFIG_SYS_MAX_FLASH_BANKS_DETECT=y
 CONFIG_DM_ETH=y
 CONFIG_PCH_GBE=y