If we are simply restarting a syscall, there's no need to do anything afterwards
to restore any register values so we don't really need to keep a record of it ourselves
in the chain syscall list.
By simply resetting the PC and the arguments, we avoid issue #292 for this function
when we get a signal before we run the restarted syscall and confused syscall
from the signal handler as the one we restarted (chained).
Yichao Yu