csky, hexagon: fix broken sys_sync_file_range

Both of these architectures require u64 function arguments to be
passed in even/odd pairs of registers or stack slots, which in case of
sync_file_range would result in a seven-argument system call that is
not currently possible. The system call is therefore incompatible with
all existing binaries.

While it would be possible to implement support for seven arguments
like on mips, it seems better to use a six-argument version, either
with the normal argument order but misaligned as on most architectures
or with the reordered sync_file_range2() calling conventions as on
arm and powerpc.

Cc: stable@vger.kernel.org
Acked-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>