Move unused function warning to gcc-unused topic branch

The ztest_pattern_match() function is only called from an ASSERT
and needs only to be defined when debugging is enabled.  This
change is to silence a gcc warning and belong with the other
gcc issues.  I'm moving it to the gcc-unused topic branch.

cmd/ztest/ztest.c

@@ -1067,7 +1067,6 @@ ztest_pattern_set(void *buf, uint64_t size, uint64_t value)
 		*ip++ = value;
 }
 
-#ifndef NDEBUG
 static boolean_t
 ztest_pattern_match(void *buf, uint64_t size, uint64_t value)
 {
@@ -1080,7 +1079,6 @@ ztest_pattern_match(void *buf, uint64_t size, uint64_t value)
 
 	return (diff == 0);
 }
-#endif
 
 static void
 ztest_bt_generate(ztest_block_tag_t *bt, objset_t *os, uint64_t object,