scripts/documentation-file-ref-check: remove some false positives

There are several false positives at tcm_mod_builder.txt:

    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_base.h
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../include/target/target_core_fabric_ops.h
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.c
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_fabric.h
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/tcm_nab5000_configfs.c
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kbuild
    Documentation/target/tcm_mod_builder.txt: mnt/sdb/lio-core-2.6.git/Documentation/target/../../drivers/target/tcm_nab5000/Kconfig

Ignore them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>