common/spl: Revert fix potential out of buffer access in spl_fit_get_image_name function

common/spl: Revert fix potential out of buffer access in spl_fit_get_image_name function

The change in commit 3704b888a4ca ("common/spl: fix potential out of buffer
access in spl_fit_get_image_name function") led to function
spl_fit_get_image_name() no longer detecting if a property does not exist
at a non-zero buffer.

Link: https://lore.kernel.org/u-boot/38f5d078-3328-4bdb-9c95-4fb5fe89ddc2@gmx.de/T/#m59f3a23e675daa992c28d12236de71cae2ca2bb9
Fixes: 3704b888a4ca ("common/spl: fix potential out of buffer access in spl_fit_get_image_name function")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Tested-by: E Shattow <e@freeshell.de>