The block IO protocol may be installed on any handle. We should make
no assumption about the structure the handle points to.
efi_disk_is_system_part() makes an illegal widening cast from a handle
to a struct efi_disk_obj. Remove the function.
Fixes: Fixes: 41fd506842 ("efi_loader: disk: add efi_disk_is_system_part()")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>