Update to v4.19 kernel headers.

Test: Builds and boots.
Change-Id: I99a9ed79666e143b47f02ca4e59eed94f69b7e4a
(cherry picked from commit a981e2e52e2e95a65fa9c9b6fb16dcb4c83dd576)
diff --git a/libc/kernel/uapi/asm-generic/unistd.h b/libc/kernel/uapi/asm-generic/unistd.h
index 39b7c1a..52f0b57 100644
--- a/libc/kernel/uapi/asm-generic/unistd.h
+++ b/libc/kernel/uapi/asm-generic/unistd.h
@@ -317,8 +317,10 @@
 #define __NR_pkey_alloc 289
 #define __NR_pkey_free 290
 #define __NR_statx 291
+#define __NR_io_pgetevents 292
+#define __NR_rseq 293
 #undef __NR_syscalls
-#define __NR_syscalls 292
+#define __NR_syscalls 294
 #if __BITS_PER_LONG == 64 && !defined(__SYSCALL_COMPAT)
 #define __NR_fcntl __NR3264_fcntl
 #define __NR_statfs __NR3264_statfs