linux-wandboard

[S390] __syscall_return error check.

Fix __syscall_return macro: valid error numbers are in the range
of -1..-4095.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>