docs: Makefile: avoid a warning when using without texlive

docs: Makefile: avoid a warning when using without texlive

As reported by Randy, running make htmldocs on a machine
without textlive now produce warnings:

    $ make O=DOCS htmldocs
    ../Documentation/Makefile:70: warning: overriding recipe for target 'pdfdocs'
    ../Documentation/Makefile:61: warning: ignoring old recipe for target 'pdfdocs'

That's because the code has now two definitions for pdfdocs in
case $PDFLATEX command is not found. With the new script, such
special case is not needed anymore, as the script checks it.

Drop the special case. Even after dropping it, on a machine
without LaTeX, it will still produce an error as expected,
as running:

    $ ./tools/docs/sphinx-build-wrapper pdfdocs
    Error: pdflatex or latexmk required for PDF generation

does the check. After applying the patch we have:

    $ make SPHINXDIRS=peci htmldocs
    Using alabaster theme
    Using Python kernel-doc

    $ make SPHINXDIRS=peci pdfdocs
    Error: pdflatex or latexmk required for PDF generation
    make[2]: *** [Documentation/Makefile:64: pdfdocs] Error 1
    make[1]: *** [/root/Makefile:1808: pdfdocs] Error 2
    make: *** [Makefile:248: __sub-make] Error 2

Which is the expected behavior.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/linux-doc/e7c29532-71de-496b-a89f-743cef28736e@infradead.org/
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <cd16a7436a510116ef87cd4abbb1f3cfe358012f.1759328070.git.mchehab+huawei@kernel.org>