sim/ppc: mark device_error function as ATTRIBUTE_NORETURN

The device_error function always ends up calling the error function,
which is itself marked as ATTRIBUTE_NORETURN, so it makes sense that
device_error should also be marked ATTRIBUTE_NORETURN.

Doing this resolves a few warnings from hw_ide.c about possibly
uninitialized variables - the variables are only uninitialized after
passing through a call to device_error, which obviously means the
variables are never really used uninitialized, the simulation will
terminate with the device_error call.