hostap: Reduce WPA supplicant heap when MbedTLS heap is enabled

If MbedTLS uses its own heap which is a static heap (not libc heap),
then WPA supplicant heap usage will come down, so, reduce 8K (minimum
MbedTLS heap for Wi-Fi) from the libc heap size.

Signed-off-by: Chaitanya Tata <Chaitanya.Tata@nordicsemi.no>
Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>
diff --git a/modules/hostap/Kconfig b/modules/hostap/Kconfig
index b5d1a52..213ab22 100644
--- a/modules/hostap/Kconfig
+++ b/modules/hostap/Kconfig
@@ -24,6 +24,8 @@
 
 config COMMON_LIBC_MALLOC_ARENA_SIZE
 	default 40000 if WIFI_NM_WPA_SUPPLICANT_AP
+	# 8192 for MbedTLS heap
+	default 21808 if MBEDTLS_ENABLE_HEAP
 	# 30K is mandatory, but might need more for long duration use cases
 	default 30000