[efi] Use long forms of device paths in debug messages

[efi] Use long forms of device paths in debug messages

We currently call ConvertDevicePathToText() with DisplayOnly=TRUE when
constructing a device path to appear within a debug message.  For
ATAPI device paths, this will unfortunately omit some key information:
the textual representation will not indicate which ATA bus or drive is
represented.  This can lead to misleading debug messages that appear
to refer to identical devices.

Fix by setting DisplayOnly=FALSE to select the long form of device
path textual representations.

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