Update to v4.17.3 kernel headers.

Test: Builds, boots on a walleye.
Change-Id: I389d8b61ec00ea309e38d1b1a2e0dace48c21edb
diff --git a/libc/kernel/uapi/asm-mips/asm/mman.h b/libc/kernel/uapi/asm-mips/asm/mman.h
index 5e8e28a..7ca4a99 100644
--- a/libc/kernel/uapi/asm-mips/asm/mman.h
+++ b/libc/kernel/uapi/asm-mips/asm/mman.h
@@ -44,6 +44,7 @@
 #define MAP_NONBLOCK 0x20000
 #define MAP_STACK 0x40000
 #define MAP_HUGETLB 0x80000
+#define MAP_FIXED_NOREPLACE 0x100000
 #define MS_ASYNC 0x0001
 #define MS_INVALIDATE 0x0002
 #define MS_SYNC 0x0004