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/P2041RDB_NAND_defconfig b/configs/P2041RDB_NAND_defconfig
index fc4eab5..10f4d71 100644
--- a/configs/P2041RDB_NAND_defconfig
+++ b/configs/P2041RDB_NAND_defconfig
@@ -76,6 +76,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_EMPTY_INFO=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=1024
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_FSL_ELBC=y
 CONFIG_DM_SPI_FLASH=y