PATCH: return signed result of syscall for cris

[Uwe Reimann]

While inspecting the file sysdeps.h I encountered a mismatch of the
comments and the code. The comments say that a return value from
-4095 to -1 indicates an error. However, the code tests the return
code to be greater or EQUAL than -4096. For the other archcitectures,
code and comments are in sync. So, I think this is another (minor)
bug.

Best regards, Uwe