scsi: core: Fix a compiler warning triggered by the SCSI logging code

This patch fixes the following compiler warning:

In file included from drivers/scsi/scsi_error.c:46:
drivers/scsi/scsi_error.c: In function 'scsi_eh_target_reset':
drivers/scsi/scsi_logging.h:65:81: warning: suggest braces around empty body in an 'if' statement [-Wempty-body]
   65 | LOGGING(SCSI_LOG_ERROR_SHIFT, SCSI_LOG_ERROR_BITS, LEVEL,CMD);
      |                                                              ^

drivers/scsi/scsi_error.c:1562:4: note: in expansion of macro 'SCSI_LOG_ERROR_RECOVERY'
 1562 |    SCSI_LOG_ERROR_RECOVERY(3,
      |    ^~~~~~~~~~~~~~~~~~~~~~~

Link: https://lore.kernel.org/r/20191209174205.190025-1-bvanassche@acm.org
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_logging.h

@@ -53,7 +53,7 @@ do {								\
 } while (0)
 #else
 #define SCSI_LOG_LEVEL(SHIFT, BITS) 0
-#define SCSI_CHECK_LOGGING(SHIFT, BITS, LEVEL, CMD)
+#define SCSI_CHECK_LOGGING(SHIFT, BITS, LEVEL, CMD) do { } while (0)
 #endif /* CONFIG_SCSI_LOGGING */
 
 /*