arm: mvebu: Use 4K sector for Thecus N2350 SPI flash

Since the SPI flash chip mx25l3205d on this board has 4K-sector
capability, enable it for the envs.

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/configs/n2350_defconfig b/configs/n2350_defconfig
index dcb2c96..b85ef0d 100644
--- a/configs/n2350_defconfig
+++ b/configs/n2350_defconfig
@@ -14,7 +14,7 @@
 CONFIG_TARGET_N2350=y
 CONFIG_ENV_SIZE=0x10000
 CONFIG_ENV_OFFSET=0x100000
-CONFIG_ENV_SECT_SIZE=0x10000
+CONFIG_ENV_SECT_SIZE=0x1000
 CONFIG_DEFAULT_DEVICE_TREE="armada-385-thecus-n2350"
 CONFIG_SPL_TEXT_BASE=0x40000030
 CONFIG_SYS_PROMPT="N2350 > "