Kconfig: fix typo in CONFIG_FIT description

Fix typo in CONFIG_FIT description - remove the accidentially added
redundand 'the'.

Signed-off-by: Igor Grinberg <grinberg@compulab.co.il>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>