arm: socfpga: gen5: reduce SPL pre-reloc malloc

By enabling debug prints in malloc_simple, we can see that SPL for socfpga
gen5 does by far not need the 8 KiB malloc pool currently allocated for
SPL in pre-reloc phase.

On socfpga_socrates, 1304 bytes are currently used (and this increases by
~200 bytes only for the sdram/reset fixes in socfpga-next).

To prevent wasting precious SRAM space, let's reduce the initial heap used
for SPL to 2 KiB. This is still some hundred bytes more than currently
used. Also, the gen5 SPL enables stack and heap in DDR memory pretty
early. Only the initial uclass/dm parsing, serial console and DDR
initialization is done in the initial heap, so these 2 KiB should be
enough for all boards.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Acked-by: Marek Vasut <marex@denx.de>
diff --git a/arch/arm/mach-socfpga/Kconfig b/arch/arm/mach-socfpga/Kconfig
index 3c6c630..8f7b79f 100644
--- a/arch/arm/mach-socfpga/Kconfig
+++ b/arch/arm/mach-socfpga/Kconfig
@@ -6,6 +6,9 @@
 config SPL_STACK_R_ADDR
 	default 0x00800000 if TARGET_SOCFPGA_GEN5
 
+config SPL_SYS_MALLOC_F_LEN
+	default 0x800 if TARGET_SOCFPGA_GEN5
+
 config SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION_TYPE
 	default 0xa2