x86/kdebugfs: Move boot params hierarchy under (debugfs)/x86/

... since this is all x86-specific data and it makes sense to have it
under x86/ logically instead in the toplevel debugfs dir.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170227225058.27289-1-bp@alien8.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>