modules: acpica: Fix header inclusion issue

After 79d0bf39 was merged, the inclusion
of <zephyr/acpi/acpi.h> with CONFIG_ACPI=n caused a build failure because
<acpica/source/include/acpi.h> could no longer be included due to the
inlcude path not being injected anymore.

Fix this by guarding the header inclusion when CONFIG_ACPI
is not set.

Fixes #62679.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>