Blackfin arch: update printk to use KERN_EMERG and reformat crash output

to look like:

return address: [0x0357fcc4]; contents of:
0x0357fca0:  fcbc  0357  fe20  0357  0009  0000  6a8c  0345
0x0357fcb0:  000e  0000  fcc4  0357  fd44  0357  e128  00ad
0x0357fcc0:  00a0  0000 [000e] 0000  0000  0000  0080  0000
0x0357fcd0:  0000  0000  0000  0000  00a0  0000  000e  0000

instruction in [] is the offending instruction

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