x86, libnvdimm, pmem: remove global pmem api

Now that all callers of the pmem api have been converted to dax helpers that
call back to the pmem driver, we can remove include/linux/pmem.h and
asm/pmem.h.

Cc: <x86@kernel.org>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Oliver O'Halloran <oohall@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/nvdimm/namespace_devs.c b/drivers/nvdimm/namespace_devs.c
index 2f9dfbd..4e9261e 100644
--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -14,10 +14,10 @@
 #include <linux/device.h>
 #include <linux/sort.h>
 #include <linux/slab.h>
-#include <linux/pmem.h>
 #include <linux/list.h>
 #include <linux/nd.h>
 #include "nd-core.h"
+#include "pmem.h"
 #include "nd.h"
 
 static void namespace_io_release(struct device *dev)
@@ -155,11 +155,7 @@ bool pmem_should_map_pages(struct device *dev)
 				IORES_DESC_NONE) == REGION_MIXED)
 		return false;
 
-#ifdef ARCH_MEMREMAP_PMEM
 	return ARCH_MEMREMAP_PMEM == MEMREMAP_WB;
-#else
-	return false;
-#endif
 }
 EXPORT_SYMBOL(pmem_should_map_pages);