uboot-imx

test/fs: Check ext4 behaviour if dirent is first entry in directory block

This is a regression test for a crash happening if the first dirent
in the block matches. Code tried to access a predecessor entry which
does not exist.
The crash happened for any block, but "." is always the first entry in
the first directory block and thus easy to check for.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>