Device paths may consist of multiple instances. Up to now we have only
considered the size of the first instance. For the services of the
EFI_DEVICE_PATH_UTILITIES_PROTOCOL in most cases the total length of the
device path is relevant.

So let's rename efi_dp_size() to efi_dp_instance_size() and create a new
function efi_dp_size() that calculates the total device path length.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Alexander Graf <agraf@suse.de>