NOR/CFI: fix memory leak; check malloc return value

NOR/CFI: fix memory leak; check malloc return value

Every time command "flash probe #" is executed, memory
structures are re-allocated without preventive free()
of former areas, causing memory leak.
Also, memory allocation does not check return value,
determining segmentation fault in case of out of memory.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Signed-off-by: Spencer Oliver <ntfreak@users.sourceforge.net>