elf: Add EM_NANOMIPS value as a valid one for e_machine field

Value 249 is registered as valid for usage for nanoMIPS executables.
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: NAleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: NAleksandar Markovic <amarkovic@wavecomp.com>
Signed-off-by: NStefan Markovic <smarkovic@wavecomp.com>

include/elf.h

@@ -143,6 +143,8 @@ typedef int64_t  Elf64_Sxword;
 
 #define EM_RISCV        243     /* RISC-V */
 
+#define EM_NANOMIPS     249     /* Wave Computing nanoMIPS */
+
 /*
  * This is an interim value that we will use until the committee comes
  * up with a final number.