ARM: UniPhier: set CONFIG_SYS_MALLOC_F to the global default value

It is true that malloc is necessary for Driver Model before
relocation, but there is no good reason to reserve the malloc
space more than enough.  The default value 0x400 works well.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>
Reviewed-by: NSimon Glass <sjg@chromium.org>

arch/arm/cpu/armv7/uniphier/Kconfig

@@ -52,7 +52,7 @@ config SYS_MALLOC_F
 	default y
 
 config SYS_MALLOC_F_LEN
-	default 0x2000
+	default 0x400
 
 config CMD_PINMON
 	bool "Enable boot mode pins monitor command"