docs: Update documentation to avoid mentioning of kernel.h

docs: Update documentation to avoid mentioning of kernel.h

For several years, and still ongoing, the kernel.h is being split
to smaller and narrow headers to avoid "including everything" approach
which is bad in many ways. Since that, documentation missed a few
required updates to align with that work. Do it here.

Note, language translations are left untouched and if anybody willing
to help, please provide path(es) based on the updated English variant.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20251126214709.2322314-1-andriy.shevchenko@linux.intel.com>