ports: Remove side effects from CC_ASSERT calls

Since p-net may be compiled without asserts
(e.g. release builds for STM32Cube), it could be
the case that expressions with side effects were
not evaluated; this would cause incorrect behaviour.

While the rt-kernel port does not use CC_ASSERT,
it has also been changed in the same manner for
consistency.

src/ports/STM32Cube/pnal.c

@@ -299,7 +299,9 @@ pnal_buf_t * pnal_buf_alloc (uint16_t length)
 
 void pnal_buf_free (pnal_buf_t * p)
 {
-   CC_ASSERT (pbuf_free (p) == 1);
+   uint8_t deallocated = pbuf_free (p);
+   (void)deallocated;
+   CC_ASSERT (deallocated == 1);
 }
 
 uint8_t pnal_buf_header (pnal_buf_t * p, int16_t header_size_increment)

src/ports/iMX8M/pnal.c

@@ -176,7 +176,9 @@ pnal_buf_t * pnal_buf_alloc (uint16_t length)
 
 void pnal_buf_free (pnal_buf_t * p)
 {
-   CC_ASSERT (pbuf_free (p) == 1);
+   uint8_t deallocated = pbuf_free (p);
+   (void)deallocated;
+   CC_ASSERT (deallocated == 1);
 }
 
 uint8_t pnal_buf_header (pnal_buf_t * p, int16_t header_size_increment)

src/ports/rt-kernel/pnal.c

@@ -369,7 +369,9 @@ pnal_buf_t * pnal_buf_alloc (uint16_t length)
 
 void pnal_buf_free (pnal_buf_t * p)
 {
-   ASSERT (pbuf_free (p) == 1);
+   uint8_t deallocated = pbuf_free (p);
+   (void)deallocated;
+   ASSERT (deallocated == 1);
 }
 
 uint8_t pnal_buf_header (pnal_buf_t * p, int16_t header_size_increment)