linux-user: Fix msgrcv() and msgsnd() syscalls support

If syscalls msgrcv() and msgsnd() fail, they return E2BIG, EACCES,
EAGAIN, EFAULT, EIDRM, EINTR, EINVAL, ENOMEM, or ENOMSG.

By examining negative scenarios of these syscalls for Mips, it was
established that ENOMSG does not have the same value accross all
platforms, but it is nevertheless not included for conversion in
the correspondant conversion table defined in linux-user/syscall.c.
This is certainly a bug, since it leads to the incorrect emulation
of msgrcv() and msgsnd() for scenarios involving ENOMSG.

This patch fixes this by extending the conversion table to include
ENOMSG.

Also, LTP test msgrcv04 will be fixed for some platforms.

Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
