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/P1020RDB-PC_NAND_defconfig b/configs/P1020RDB-PC_NAND_defconfig
index fd5afad..60cb1ad 100644
--- a/configs/P1020RDB-PC_NAND_defconfig
+++ b/configs/P1020RDB-PC_NAND_defconfig
@@ -111,6 +111,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_EMPTY_INFO=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=128
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_FSL_ELBC=y
 CONFIG_SYS_NAND_BLOCK_SIZE=0x4000