MIPS: Prevent compiler warning from cop2_{save,restore}

The no-op cases of cop2_save & cop2_restore lead to the following
warnings being emitted during build with recent versions of gcc (tested
using gcc 4.8.3 from the Mentor Sourcery CodeBench 2014.05 toolchain):

In file included from ./arch/mips/include/asm/switch_to.h:18:0,
from kernel/sched/core.c:78:
kernel/sched/core.c: In function 'finish_task_switch':
include/asm-generic/current.h:6:45: warning: value computed is not used [-Wunused-value]
#define get_current() (current_thread_info()->task)
^
./arch/mips/include/asm/cop2.h:48:32: note: in definition of macro 'cop2_restore'
#define cop2_restore(r) do { (r); } while (0)
^
include/asm-generic/current.h:7:17: note: in expansion of macro 'get_current'
#define current get_current()
^
./arch/mips/include/asm/switch_to.h:114:16: note: in expansion of macro 'current'
cop2_restore(current); \
^
kernel/sched/core.c:2225:2: note: in expansion of macro 'finish_arch_switch'
finish_arch_switch(prev);
^

Avoid the warning by "using" the value by casting to void.

Signed-off-by: Paul Burton <[e-mail]>
Cc: [e-mail]
Patchwork: https://patchwork.linux-mips.org/patch/7880/
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/include/asm/cop2.h

···
 
 #define cop2_present		1
 #define cop2_lazy_restore	1
-#define cop2_save(r)		do { (r); } while (0)
-#define cop2_restore(r)		do { (r); } while (0)
+#define cop2_save(r)		do { (void)(r); } while (0)
+#define cop2_restore(r)		do { (void)(r); } while (0)
 
 #else
 
 #define cop2_present		0
 #define cop2_lazy_restore	0
-#define cop2_save(r)		do { (r); } while (0)
-#define cop2_restore(r)		do { (r); } while (0)
+#define cop2_save(r)		do { (void)(r); } while (0)
+#define cop2_restore(r)		do { (void)(r); } while (0)
 #endif
 
 enum cu2_ops {