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/total_compute_defconfig b/configs/total_compute_defconfig
index 43db639..ab13ac8 100644
--- a/configs/total_compute_defconfig
+++ b/configs/total_compute_defconfig
@@ -56,5 +56,6 @@
 CONFIG_SYS_FLASH_EMPTY_INFO=y
 CONFIG_SYS_FLASH_PROTECTION=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=256
 CONFIG_LIBAVB=y
 CONFIG_OF_LIBFDT_OVERLAY=y