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/10m50_defconfig b/configs/10m50_defconfig
index 6c56cdc..5083545 100644
--- a/configs/10m50_defconfig
+++ b/configs/10m50_defconfig
@@ -40,6 +40,7 @@
 CONFIG_DM_MTD=y
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_ALTERA_QSPI=y
+CONFIG_SYS_MAX_FLASH_SECT=1024
 CONFIG_PHY_MARVELL=y
 CONFIG_DM_ETH=y
 CONFIG_PHY_GIGE=y