mips: split syscallent.h

linux/mips/syscallent.h consisted of several parts that had little in
common.  Split them into separate files to ease maintenance.

* linux/mips/syscallent-compat.h: New file.
* linux/mips/syscallent-n32.h: Likewise.
* linux/mips/syscallent-n64.h: Likewise.
* linux/mips/syscallent-o32.h: Likewise.
* linux/mips/syscallent.h: Include them.
* Makefile.am (EXTRA_DIST): Add them.
diff --git a/Makefile.am b/Makefile.am
index 9bbda66..639430d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -105,6 +105,10 @@
 	linux/mips/ioctlent.h.in	\
 	linux/mips/ioctlent.sh		\
 	linux/mips/signalent.h		\
+	linux/mips/syscallent-compat.h	\
+	linux/mips/syscallent-n32.h	\
+	linux/mips/syscallent-n64.h	\
+	linux/mips/syscallent-o32.h	\
 	linux/mips/syscallent.h		\
 	linux/mtd-abi.h			\
 	linux/powerpc/errnoent1.h	\