psa: Add PSA Crypto configuration

Add an option that can enable the exposure of PSA Crypto APIs from
libmbedcrypto.
diff --git a/scripts/config.pl b/scripts/config.pl
index 3d2884c..085fc2c 100755
--- a/scripts/config.pl
+++ b/scripts/config.pl
@@ -28,6 +28,7 @@
 #   MBEDTLS_ECP_DP_M511_ENABLED
 #   MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
 #   MBEDTLS_NO_PLATFORM_ENTROPY
+#   MBEDTLS_PSA_CRYPTO_C
 #   MBEDTLS_REMOVE_ARC4_CIPHERSUITES
 #   MBEDTLS_SSL_HW_RECORD_ACCEL
 #   MBEDTLS_RSA_NO_CRT
@@ -87,6 +88,7 @@
 MBEDTLS_ECP_DP_M511_ENABLED
 MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
 MBEDTLS_NO_PLATFORM_ENTROPY
+MBEDTLS_PSA_CRYPTO_C
 MBEDTLS_RSA_NO_CRT
 MBEDTLS_REMOVE_ARC4_CIPHERSUITES
 MBEDTLS_SSL_HW_RECORD_ACCEL