Blackfin arch: Fix up /proc/cpuinfo so it is like everyone else

Fix up /proc/cpuinfo so it is like everyone else, and gets
parsed by various applications properly. Still needs some tweaking on
parts without full L1 sram, like 532, 531, so it doesn't print out L1
bank info that doesn't exist.

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