x86/mm/pat: Drop the rbt_ prefix from external memtype calls

Drop the rbt_memtype_*() call rbt_ prefix, as we no longer use
an rbtree directly.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20191121011601.20611-4-dave@stgolabs.net


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