Documentation/arch/ia64/features.rst: fix kernel-feat directive

My mainline commit c48a7c44 ("docs: kernel_feat.py: fix potential
command injection") contains a bug which can manifests like this when
building the documentation:

    Sphinx parallel build error:
    UnboundLocalError: local variable 'fname' referenced before assignment
    make[2]: *** [Documentation/Makefile:102: htmldocs] Error 2

However, this only appears when there exists a '.. kernel-feat::'
directive that points to a non-existent file, which isn't the case in
mainline.

When this commit was backported to stable 6.6, it didn't change
Documentation/arch/ia64/features.rst since ia64 was removed in 6.7 in
commit cf8e8658 ("arch: Remove Itanium (IA-64) architecture"). This
lead to the build failure seen above -- but only in stable kernels.

This patch fixes the backport and should only be applied to kernels where
Documentation/arch/ia64/features.rst exists and commit c48a7c44 has
also been applied.

A second patch will follow to fix kernel_feat.py in mainline so that it
doesn't error out when the '.. kernel-feat::' directive points to a
nonexistent file.

Link: https://lore.kernel.org/all/ZbkfGst991YHqJHK@fedora64.linuxtx.org/
Fixes: e961f8c6

 ("docs: kernel_feat.py: fix potential command injection") # stable 6.6.15
Reported-by: Justin Forbes <jforbes@fedoraproject.org>
Reported-by: Salvatore Bonaccorso <carnil@debian.org>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>