CFI: avoid redundant function call in single word programming mode

The function find_sector() doesn't need to be called twice in
the case of AMD command set.
Tested on TQM5200S-BD with Samsung K8P2815UQB.

Signed-off-by: Jens Gehrlein <sew_s@tqs.de>
Signed-off-by: Stefan Roese <sr@denx.de>