Correct logic to exclude i386 inline assenbly when -O0
The i386 MPI inline assembly code was being incorrectly included when
all compiler optimisation was disabled.
diff --git a/include/mbedtls/bn_mul.h b/include/mbedtls/bn_mul.h
index 438aa8c..b587317 100644
--- a/include/mbedtls/bn_mul.h
+++ b/include/mbedtls/bn_mul.h
@@ -56,7 +56,7 @@
* This is done as the number of registers used in the assembly code doesn't
* work with the -O0 option.
*/
-#if defined(__i386__) && !defined(__OPTIMIZE__)
+#if defined(__i386__) && defined(__OPTIMIZE__)
#define MULADDC_INIT \
asm( \