Create generic 64-bit syscallent.h

Create generic 64-bit syscallent.h

Since aarch64/syscallent1.h and tile/syscallent.h share a lot of
identical syscall entries described in <asm-generic/unistd.h>, move
these entries to a new file 64/syscallent.h using the following
automated conversion with subsequent correction of whitespace
indentation:

sed -e 's|^[[:space:]]*\({[^}]\+},\)[[:space:]]*/\*[[:space:]]\([[:space:]]*[0-9]\+\)[[:space:]]*\*/|[\2] = \1|' -e '/^\[[[:space:]]*2\(4[4-9]\|5[0-9]\)\]/d' linux/tile/syscallent.h

* linux/64/syscallent.h: New file.
* Makefile.am (EXTRA_DIST): Add it.
* linux/aarch64/syscallent1.h: Include "64/syscallent.h",
remove generic 64-bit syscall entries, use designated initializers.
* linux/tile/syscallent.h: Likewise.