Update to v4.17.3 kernel headers.

Test: Builds, boots on a walleye.
Change-Id: I389d8b61ec00ea309e38d1b1a2e0dace48c21edb
diff --git a/libc/kernel/uapi/linux/eventpoll.h b/libc/kernel/uapi/linux/eventpoll.h
index eec1077..2e5ba8e 100644
--- a/libc/kernel/uapi/linux/eventpoll.h
+++ b/libc/kernel/uapi/linux/eventpoll.h
@@ -25,21 +25,22 @@
 #define EPOLL_CTL_ADD 1
 #define EPOLL_CTL_DEL 2
 #define EPOLL_CTL_MOD 3
-#define EPOLLIN 0x00000001
-#define EPOLLPRI 0x00000002
-#define EPOLLOUT 0x00000004
-#define EPOLLERR 0x00000008
-#define EPOLLHUP 0x00000010
-#define EPOLLRDNORM 0x00000040
-#define EPOLLRDBAND 0x00000080
-#define EPOLLWRNORM 0x00000100
-#define EPOLLWRBAND 0x00000200
-#define EPOLLMSG 0x00000400
-#define EPOLLRDHUP 0x00002000
-#define EPOLLEXCLUSIVE (1U << 28)
-#define EPOLLWAKEUP (1U << 29)
-#define EPOLLONESHOT (1U << 30)
-#define EPOLLET (1U << 31)
+#define EPOLLIN (__force __poll_t) 0x00000001
+#define EPOLLPRI (__force __poll_t) 0x00000002
+#define EPOLLOUT (__force __poll_t) 0x00000004
+#define EPOLLERR (__force __poll_t) 0x00000008
+#define EPOLLHUP (__force __poll_t) 0x00000010
+#define EPOLLNVAL (__force __poll_t) 0x00000020
+#define EPOLLRDNORM (__force __poll_t) 0x00000040
+#define EPOLLRDBAND (__force __poll_t) 0x00000080
+#define EPOLLWRNORM (__force __poll_t) 0x00000100
+#define EPOLLWRBAND (__force __poll_t) 0x00000200
+#define EPOLLMSG (__force __poll_t) 0x00000400
+#define EPOLLRDHUP (__force __poll_t) 0x00002000
+#define EPOLLEXCLUSIVE (__force __poll_t) (1U << 28)
+#define EPOLLWAKEUP (__force __poll_t) (1U << 29)
+#define EPOLLONESHOT (__force __poll_t) (1U << 30)
+#define EPOLLET (__force __poll_t) (1U << 31)
 #ifdef __x86_64__
 #define EPOLL_PACKED __attribute__((packed))
 #else