arc: convert to generic syscall table

The uapi/asm/unistd_32.h and asm/syscall_table_32.h headers can now be
generated from scripts/syscall.tbl, which makes this consistent with
the other architectures that have their own syscall.tbl.

arc has a couple of architecture specific system calls, which I add to the
generic table. This for some reason includes the deprecated sys_sysfs()
syscall that was presumably added by accident.

The time32, renameat, stat64 and rlimit entries in the syscall_abis_32
entry are for system calls that were part of the generic ABI when arch/arc
got added but are no longer enabled by default for new architectures.

Both the user visible side of asm/unistd.h and the internal syscall
table in the kernel should have the same effective contents after this.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>