x86/Kconfig: Make X86_FEATURE_NAMES non-configurable in prompt

While discussing to change the visibility of X86_FEATURE_NAMES (see Link)
in order to remove CONFIG_EMBEDDED, Boris suggested to simply make the
X86_FEATURE_NAMES functionality unconditional.

As a first step, make X86_FEATURE_NAMES disappear from Kconfig. So, as
X86_FEATURE_NAMES defaults to yes, to disable it, one now needs to
modify the .config file before compiling the kernel.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/all/20230509084007.24373-1-lukas.bulwahn@gmail.com/