Blackfin arch: Enable earlyprintk earlier - so any error after our interrupt tables are set up will print out

Also ensure that the traps_c code doesn't cause a double fault, by
sending a signal to a faulting kernel before the memory subsystem
is fully initialized, by printing out the error message before sending
the signal.
Signed-off-by: NRobin Getz <robin.getz@analog.com>
Signed-off-by: NBryan Wu <bryan.wu@analog.com>