Avoid unused variable warnings in case __ASSERT evaluates to NOP.

.gitmodules

@@ -1,3 +1,4 @@
 [submodule "utils"]
 	path = utils
-	url = https://github.com/goToMain/c-utils.git
+	url = https://github.com/rustylocker/c-utils.git
+	branch = fix-zephyr-and-gcc-build-issues

src/osdp_cp.c

@@ -181,6 +181,8 @@ static inline void assert_buf_len(int need, int have)
 {
 	__ASSERT(need < have, "OOM at build command: need:%d have:%d",
 		 need, have);
+	(void)need;
+	(void)have;
 }
 
 static int cp_build_command(struct osdp_pd *pd, uint8_t *buf, int max_len)

src/osdp_pd.c

@@ -748,6 +748,8 @@ static inline void assert_buf_len(int need, int have)
 {
 	__ASSERT(need < have, "OOM at build command: need:%d have:%d",
 		 need, have);
+	(void)need;
+	(void)have;
 }
 
 /**