x86/mm/pat: Rename pat_rbtree.c to pat_interval.c

Considering the previous changes, this is a more proper name.
Signed-off-by: Davidlohr Bueso <dbueso@suse.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/20191121011601.20611-5-dave@stgolabs.netSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/Makefile

@@ -23,7 +23,7 @@ CFLAGS_mem_encrypt_identity.o	:= $(nostackp)
 
 CFLAGS_fault.o := -I $(srctree)/$(src)/../include/asm/trace
 
-obj-$(CONFIG_X86_PAT)		+= pat_rbtree.o
+obj-$(CONFIG_X86_PAT)		+= pat_interval.o
 
 obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o