Update signature of mbedtls_platform_random_delay

Skip parameter and return value from mbedtls_platform_random_delay
to make it more resistant for FI attacks.
diff --git a/library/pk.c b/library/pk.c
index 252c789..caa5e17 100644
--- a/library/pk.c
+++ b/library/pk.c
@@ -597,7 +597,7 @@
 
     if( ret_fi == UECC_SUCCESS )
     {
-        mbedtls_platform_random_delay( 50 );
+        mbedtls_platform_random_delay();
         if( ret_fi == UECC_SUCCESS )
             return( 0 );
         else
@@ -1553,7 +1553,7 @@
 
     if( verify_ret == 0 )
     {
-        mbedtls_platform_random_delay(50);
+        mbedtls_platform_random_delay();
         if( verify_ret == 0 )
         {
             return( verify_ret );