[SPARC64]: Fix arg passing to compat_sys_ipc().

Do not sign extend args using the sys32_ipc stub, that is
buggy and unnecessary.

Based upon an excellent report by Mikael Pettersson.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>