soc/intel/cannonlake: Increase heap size

After adding NHLT and max98373 amp support, cnlrvp fails to boot
with error: out of memory (free_mem_ptr >= free_mem_end_ptr).
Increase HEAP_SIZE from 0x4000 to 0x8000.

BUG=None
TEST= emerge-cnlrvp coreboot nhlt-blobs chromeos-bootimage coreboot-private-files-cnlrvp
and verify cnlrvp boots to kernel.

Change-Id: Icb0f3c626b784d73e417e5722b3b4da29ab5acce
Signed-off-by: John Zhao <john.zhao@intel.com>
Reviewed-on: https://review.coreboot.org/23560
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/soc/intel/cannonlake/Kconfig

@@ -115,6 +115,10 @@ config IED_REGION_SIZE
 	hex
 	default 0x400000
 
+config HEAP_SIZE
+	hex
+	default 0x8000
+
 config NHLT_DMIC_1CH_16B
 	bool
 	depends on ACPI_NHLT