posix: Remove static assertion

Standard C does not allow pointer operands in an integer constant
expressions.  GCC issues only a -Wpedantic warning in the removed static
assertion.  However, clang is pedantic by default and issues an error.

Rely on the test case instead.

cpukit/posix/src/seminit.c

@@ -22,8 +22,6 @@
 
 #include <limits.h>
 
-RTEMS_STATIC_ASSERT(NULL == SEM_FAILED, sem_failed);
-
 /*
  *  11.2.1 Initialize an Unnamed Semaphore, P1003.1b-1993, p.219
  */

testsuites/psxtests/psxsem01/init.c

@@ -193,6 +193,7 @@ static void test_sem_null(void)
   int val;
   struct timespec to;
 
+  /* This equality is important for POSIX_SEMAPHORE_VALIDATE_OBJECT() */
   rtems_test_assert( NULL == SEM_FAILED );
 
   errno = 0;