Revert "Increase default of CONFIG_SYS_MALLOC_F_LEN for SPL_OF_CONTROL"

This reverts commit 90c08d9e08c7a108ab904f3bbdeb558081757892.

I took a closer look at this after the commit was applied, and found
CONFIG_SYS_MALLOC_F_LEN=0x2000 was too much.  8KB memory for SPL is
actually too big for some boards.  Perhaps 0x800 is enough, but the
situation varies board by board.

Let's postpone our decision until we come up with a better idea.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/socfpga_de0_nano_soc_defconfig b/configs/socfpga_de0_nano_soc_defconfig
index 479f334..fa174be 100644
--- a/configs/socfpga_de0_nano_soc_defconfig
+++ b/configs/socfpga_de0_nano_soc_defconfig
@@ -1,5 +1,6 @@
 CONFIG_ARM=y
 CONFIG_ARCH_SOCFPGA=y
+CONFIG_SYS_MALLOC_F_LEN=0x2000
 CONFIG_TARGET_SOCFPGA_TERASIC_DE0_NANO=y
 CONFIG_SPL_STACK_R_ADDR=0x00800000
 CONFIG_DEFAULT_DEVICE_TREE="socfpga_cyclone5_de0_nano_soc"