dracut: Implement ACPI table overriding

dracut: Implement ACPI table overriding

An example config file for this feature could be:

/etc/dracut.conf.d/03-acpi-override.conf

with this content:
acpi_override="yes"
acpi_table_dir="/etc/dracut.conf.d/acpi_tables"

Then all files ending with *.aml will be put into the early cpio
(kernel/firmware/acpi) and will be used to replace the BIOS provided tables
if the kernel supports this feature.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>