This patch adds a bunch of missing syscalls to AVR32:
__NR_pread64
__NR_pwrite64
__NR_timerfd_create
__NR_fallocate
__NR_timerfd_settime
__NR_timerfd_gettime
__NR_signalfd4
__NR_eventfd2
__NR_epoll_create1
__NR_dup3
__NR_pipe2
__NR_inotify_init1
__NR_preadv
__NR_pwritev
__NR_rt_tgsigqueueinfo
__NR_perf_event_open
__NR_recvmmsg
__NR_fanotify_init
__NR_fanotify_mark
__NR_prlimit64
__NR_name_to_handle_at
__NR_open_by_handle_at
__NR_clock_adjtime
__NR_syncfs
__NR_sendmmsg
__NR_process_vm_readv
__NR_process_vm_writev
__NR_kcmp
__NR_finit_module
__NR_sched_setattr
__NR_sched_getattr
__NR_renameat2
__NR_seccomp
__NR_getrandom
__NR_memfd_create
__NR_bpf
__NR_execveat

On AVR32, all parameters beyond the 5th are passed on the stack. System
calls don't use the stack -- they borrow a callee-saved register
instead. This means that syscalls that take 6 parameters must be called
through a stub that pushes the last parameter on the stack.

This relates to syscall fallocate, fanotify_mark, process_vm_readv, and
process_vm_writev.
Signed-off-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>