memory: tegra: Delete dead debugfs checking code

The debugfs_create_dir() function does not return NULL, it returns error
pointers.  But in normal situations like this where the caller is not
dereferencing "emc->debugfs.root" then we are not supposed to check the
return.  So instead of fixing these checks, we should delete them.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YMCQDTSyG8UuQoh0@mwanda
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>