MIPS: Remove unused CAT macro

asm/asm.h provides a CAT macro which is unused throughout the tree, and
if anyone wanted it the generic CONCATENATE macro in linux/kernel.h
provides the same functionality. Delete the dead code.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20905/
Cc: linux-mips@linux-mips.org

arch/mips/include/asm/asm.h

@@ -20,15 +20,6 @@
 #include <asm/sgidefs.h>
 #include <asm/asm-eva.h>
 
-#ifndef CAT
-#ifdef __STDC__
-#define __CAT(str1, str2) str1##str2
-#else
-#define __CAT(str1, str2) str1/**/str2
-#endif
-#define CAT(str1, str2) __CAT(str1, str2)
-#endif
-
 /*
  * LEAF - declare leaf routine
  */