[nrf noup] Align heap configuration to Wi-Fi needs

Force the default value of the libc heap to remain dynamic
instead of propagating 30k of pre-reserved pool from wpa_supplicat.
Also align the sys_heap pool to match the default Wi-Fi heap size.

Signed-off-by: Marcin Kajor <marcin.kajor@nordicsemi.no>

config/nrfconnect/chip-module/Kconfig.defaults

@@ -55,9 +55,13 @@ config HEAP_MEM_POOL_SIZE
     default 80000 if CHIP_WIFI
 
 config CHIP_MALLOC_SYS_HEAP_SIZE
-    default 28672 if CHIP_WIFI
+    default 30720 if CHIP_WIFI
     default 8192 if NET_L2_OPENTHREAD
 
+# We use sys_heap based allocators, so make sure we don't reserve unused libc heap anyway
+config COMMON_LIBC_MALLOC_ARENA_SIZE
+    default -1
+
 config NVS_LOOKUP_CACHE_SIZE
     default 512