bsd-user: replace fprintf(stderr, ...) with error_report()

Replace fprintf(stderr,...) with error_report() in files bsd-user/*.
The trailing "\n"s of the @fmt argument have been removed
because @fmt of error_report() should not contain newline.

Signed-off-by: Le Tan <tamlokveer@gmail.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>