fix POLLWRNORM and POLLWRBAND on mips

these macros have the same distinct definition on blackfin, frv, m68k,
mips, sparc and xtensa kernels. POLLMSG and POLLRDHUP additionally
differ on sparc.

arch/mips/bits/poll.h

@@ -0,0 +1,2 @@
+#define POLLWRNORM POLLOUT
+#define POLLWRBAND 0x100

include/poll.h

@@ -7,6 +7,8 @@ extern "C" {
 
 #include <features.h>
 
+#include <bits/poll.h>
+
 #define POLLIN     0x001
 #define POLLPRI    0x002
 #define POLLOUT    0x004
@@ -15,10 +17,14 @@ extern "C" {
 #define POLLNVAL   0x020
 #define POLLRDNORM 0x040
 #define POLLRDBAND 0x080
+#ifndef POLLWRNORM
 #define POLLWRNORM 0x100
 #define POLLWRBAND 0x200
+#endif
+#ifndef POLLMSG
 #define POLLMSG    0x400
 #define POLLRDHUP  0x2000
+#define
 
 typedef unsigned long nfds_t;