Update to v4.20.1 kernel headers.

This includes one manual change:

In the file bionic/libc/kernel/uapi/linux/in.h, the macro IN_BADCLASS
was not definied correctly. Change the macro from:

  #define IN_BADCLASS(a) ((((long int) (a)) == 0xffffffff)

to:

  #define IN_BADCLASS(a) (((long int) (a)) == (long int)0xffffffff)

This change is being pushed to the upstream kernels.

Test: Builds and boots.
Change-Id: Ia304773a9dc6789b34d9769d73742384d6afb571
Merged-In: Ia304773a9dc6789b34d9769d73742384d6afb571
(cherry picked from commit 967fb01cce73591281e7804e2c0fa9f83b618f5b)
diff --git a/libc/kernel/uapi/linux/elf-em.h b/libc/kernel/uapi/linux/elf-em.h
index b7c89da..5b54e18 100644
--- a/libc/kernel/uapi/linux/elf-em.h
+++ b/libc/kernel/uapi/linux/elf-em.h
@@ -52,6 +52,7 @@
 #define EM_TILEPRO 188
 #define EM_MICROBLAZE 189
 #define EM_TILEGX 191
+#define EM_RISCV 243
 #define EM_BPF 247
 #define EM_FRV 0x5441
 #define EM_ALPHA 0x9026