bpf, elf: add official ELF machine define for eBPF

Add the official BPF ELF e_machine value that was assigned recently [1,2]
and will be propagated to glibc, et al. LLVM is switching to it in 3.9
release.

[1] https://github.com/llvm-mirror/llvm/commit/36b9c09330bfb5e771914cfe307588f30d5510d2
[2] http://lists.iovisor.org/pipermail/iovisor-dev/2016-June/000266.html

Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Alexei Starovoitov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/elf-em.h

···
 #define EM_TILEPRO	188	/* Tilera TILEPro */
 #define EM_MICROBLAZE	189	/* Xilinx MicroBlaze */
 #define EM_TILEGX	191	/* Tilera TILE-Gx */
+#define EM_BPF		247	/* Linux BPF - in-kernel virtual machine */
 #define EM_FRV		0x5441	/* Fujitsu FR-V */
 #define EM_AVR32	0x18ad	/* Atmel AVR32 */