ibft: For UEFI machines actually do scan ACPI for iBFT.

For machines with IBFT 1.03 do scan the ACPI table for 'iBFT'
or for 'IBFT'. If the machine is in UEFI mode, only do the ACPI
table scan. For all other machines (pre IBFT 1.03) do
a memory scan if not found in the ACPI tables.

Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
Tested-by: Mike Christie <michaelc@cs.wisc.edu>