powerpc/eeh: Remove misleading test in eeh_handle_normal_event()

Remove a test that checks if "frozen_bus" is NULL, because it cannot
have changed since it was tested at the start of the function and so
must be true here.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>