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/P1010RDB-PB_SPIFLASH_defconfig b/configs/P1010RDB-PB_SPIFLASH_defconfig
index 7915c8f..33f2840 100644
--- a/configs/P1010RDB-PB_SPIFLASH_defconfig
+++ b/configs/P1010RDB-PB_SPIFLASH_defconfig
@@ -93,6 +93,7 @@
 CONFIG_SYS_FLASH_USE_BUFFER_WRITE=y
 CONFIG_SYS_FLASH_EMPTY_INFO=y
 CONFIG_SYS_FLASH_CFI=y
+CONFIG_SYS_MAX_FLASH_SECT=256
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SF_DEFAULT_SPEED=10000000
 CONFIG_SPI_FLASH_SPANSION=y