Blackfin arch: cleanup arch/blackfin/kernel/traps.c handling code.

 - move the CONFIG_KGDB into one block, for easier reading
 - remove printk from printk_address, and pass around buffers. Also
   print out the labels when decoding CPLB errors, so you know exactly
   where the error was.
 - Do not use fixed addresses, becuase people do not know where they come from.
 - Turn the printing level down on the dump, so if you don't want,
   only the signal prints out - just like on other archs. If a kernel/interrupt
   crashes, it should dump everything all the time

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>