elf-em.h: Define and explain both EM_MIPS_RS3_LE and EM_MIPS_RS4_BE.

They have been obsoleted by the ELF header EI_CLASS and EI_DATA fields
in combination with e_flags.  Afaics EM_MIPS_RS3_LE and EM_MIPS_RS4_BE
never had any practical relevance.  Binutils will not produce such
binaries and the kernel will not accept them as MIPS binaries.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/linux/elf-em.h

@@ -11,7 +11,12 @@
 #define EM_486		6	/* Perhaps disused */
 #define EM_860		7
 #define EM_MIPS		8	/* MIPS R3000 (officially, big-endian only) */
+				/* Next two are historical and binaries and
+				   modules of these types will be rejected by
+				   Linux.  */
+#define EM_MIPS_RS3_LE	10	/* MIPS R3000 little-endian */
 #define EM_MIPS_RS4_BE	10	/* MIPS R4000 big-endian */
+
 #define EM_PARISC	15	/* HPPA */
 #define EM_SPARC32PLUS	18	/* Sun's "v8plus" */
 #define EM_PPC		20	/* PowerPC */