Documentation: Merge x86-specific boot options doc into kernel-parameters.txt

Documentation/arch/x86/x86_64/boot-options.rst is causing unnecessary
confusion by being a second place where one can put x86 boot options.
Move them into the main one.

Drop removed ones like "acpi=ht", while at it.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20241202190011.11979-1-bp@kernel.org