add comment to explain why (-1 * rc) is returned

Author: Netanel Gonen

features/mbedtls/platform/TARGET_PSA/COMPONENT_PSA_SRV_IMPL/src/default_random_seed.cpp

@@ -5,13 +5,21 @@
 
 int mbed_default_seed_read(unsigned char *buf, size_t buf_len)
 {
+    /* Make sure that in case of an error the value will be negative
+     * return (-1 * rc);
+     * Mbed TLS errors are negative values
+     */
     psa_its_status_t rc = psa_its_get(PSA_CRYPTO_ITS_RANDOM_SEED_UID, 0, buf_len, buf);
     return ( -1 * rc );
 }
 
 int mbed_default_seed_write(unsigned char *buf, size_t buf_len)
 {
     psa_its_status_t rc = psa_its_set(PSA_CRYPTO_ITS_RANDOM_SEED_UID, buf_len, buf, 0);
+    /* Make sure that in case of an error the value will be negative
+     * return (-1 * rc);
+     * Mbed TLS errors are negative values
+     */
     return ( -1 * rc );
 }