arm64: zynqmp: Decrease MALLOC size for SPL

Decrease malloc size to 1MB from 256MB. Huge malloc
space is adding huge delay in mem_malloc_init() because
we are enabling CONFIG_SYS_MALLOC_CLEAR_ON_INIT
which clear the whole malloc space.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

include/configs/xilinx_zynqmp.h

@@ -289,7 +289,7 @@
 # define CONFIG_ENV_MAX_ENTRIES	10
 
 # define CONFIG_SYS_SPL_MALLOC_START	0x20000000
-# define CONFIG_SYS_SPL_MALLOC_SIZE	0x10000000
+# define CONFIG_SYS_SPL_MALLOC_SIZE	0x100000
 
 #ifdef CONFIG_SPL_SYS_MALLOC_SIMPLE
 # error "Disable CONFIG_SPL_SYS_MALLOC_SIMPLE. Full malloc needs to be used"