[IA64] Allow salinfo_decode to detect signals on read

Return -EINTR instead of -ERESTARTSYS when signals are delivered during
a blocked read of /proc/sal/*/event.  This allows salinfo_decode to
detect signals when it is blocked on a read of those files.

Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>