[efi] Move abstract device path and handle functions to efi_utils.c

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Generalise snpnet_pci_info() to efi_locate_device()

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[bios] Support displaying and hiding cursor

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[efi] Support displaying and hiding cursor

Signed-off-by: Michael Brown <mcb30@ipxe.org>
[readline] Ensure cursor is visible when prompting for input

Signed-off-by: Michael Brown <mcb30@ipxe.org>