doc: imx: habv4: Remove extra hab directory for a cleaner documentation structure

There is no need to have an extra hab directory under doc/imx/.

Habv4 and AHAB documentation can be added directly in doc/imx/ for a
cleaner documentation structure.

Signed-off-by: Breno Lima <breno.lima@nxp.com>

diff --git a/doc/imx/hab/habv4/encrypted_boot.txt b/doc/imx/habv4/encrypted_boot.txt
similarity index 100%
rename from doc/imx/hab/habv4/encrypted_boot.txt
rename to doc/imx/habv4/encrypted_boot.txt

diff --git a/doc/imx/hab/habv4/secure_boot.txt b/doc/imx/habv4/secure_boot.txt
similarity index 100%
rename from doc/imx/hab/habv4/secure_boot.txt
rename to doc/imx/habv4/secure_boot.txt