cfi: simplify and clearify code

cfi: simplify and clearify code

At the end I have added comments /* FIXME: to be removed */
There are 3 lines in which my simplification is not complete due to
data dependency with LOG_DEBUG() messages visible in the patch.
Such log_debug has been introduced on Jan 22, 2007 with commit
4fc97d3f2726efa147cfdb0c456eace51550e1e3 during development activity
in this file/procedure.

From my point of view, these logs can be removed, since not part of a
consistent flow of information.
Alternatively, could be borrowed in the new cfi_send_command(), but
this will increase verbosity.

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>