Makefile: Use common code for LIBATA deprecation warning

Update the CONFIG_LIBATA check to use the 'deprecated' function.

Tested with MPC8349ITX

Old message:

===================== WARNING ======================
This board does use CONFIG_LIBATA but has CONFIG_AHCI not
enabled. Please update the storage controller driver to use
CONFIG_AHCI before the v2019.07 release.
Failure to update by the deadline may result in board removal.
See doc/driver-model/migration.rst for more info.
====================================================

New message:

===================== WARNING ======================
This board does not use CONFIG_AHCI (Driver Model
for AHCI). Please update the board to use
CONFIG_AHCI before the v2019.07 release. Failure to
update by the deadline may result in board removal.
See doc/driver-model/migration.rst for more info.
====================================================

Signed-off-by: Simon Glass <sjg@chromium.org>