nvmem: Move nvmem code in dev/nvmem

We've removed kernel option EXT_RESOURCES almost two years ago.
While it was ok to have some code under a common 'extres' subdirectory
at first, we now have a lot of consumer of it and we made it mandatory
so no need to have it under a cryptic name.

Reviewed by:	dab, imp
Sponsored by:   Beckhoff Automation GmbH & Co. KG
Differential Revision:	https://reviews.freebsd.org/D43193

sys/arm/allwinner/aw_thermal.c

@@ -45,7 +45,7 @@
 
 #include <dev/clk/clk.h>
 #include <dev/hwreset/hwreset.h>
-#include <dev/extres/nvmem/nvmem.h>
+#include <dev/nvmem/nvmem.h>
 
 #include <arm/allwinner/aw_sid.h>
 

sys/conf/files

@@ -1682,8 +1682,6 @@ dev/extres/phy/phydev_if.m	optional phy fdt
 dev/extres/phy/phynode_if.m	optional phy
 dev/extres/phy/phy_usb.c	optional phy
 dev/extres/phy/phynode_usb_if.m	optional phy
-dev/extres/nvmem/nvmem.c	optional nvmem fdt
-dev/extres/nvmem/nvmem_if.m	optional nvmem
 dev/extres/regulator/regdev_if.m	optional regulator fdt
 dev/extres/regulator/regnode_if.m	optional regulator
 dev/extres/regulator/regulator.c	optional regulator
@@ -2531,6 +2529,8 @@ dev/nvme/nvme_sim.c		optional nvme scbus
 dev/nvme/nvme_sysctl.c		optional nvme
 dev/nvme/nvme_test.c		optional nvme
 dev/nvme/nvme_util.c		optional nvme
+dev/nvmem/nvmem.c		optional nvmem fdt
+dev/nvmem/nvmem_if.m		optional nvmem
 dev/oce/oce_hw.c		optional oce pci
 dev/oce/oce_if.c		optional oce pci
 dev/oce/oce_mbox.c		optional oce pci

sys/dev/nvmem/nvmem.h

@@ -23,8 +23,8 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _DEV_EXTRES_NVMEM_H_
-#define _DEV_EXTRES_NVMEM_H_
+#ifndef _DEV_NVMEM_H_
+#define	_DEV_NVMEM_H_
 
 int nvmem_get_cell_len(phandle_t node, const char *name);
 int nvmem_read_cell_by_name(phandle_t node, const char *name, void *cell, size_t buflen);
@@ -32,4 +32,4 @@ int nvmem_read_cell_by_idx(phandle_t node, int idx, void *cell, size_t buflen);
 int nvmem_write_cell_by_name(phandle_t node, const char *name, void *cell, size_t buflen);
 int nvmem_write_cell_by_idx(phandle_t node, int idx, void *cell, size_t buflen);
 
-#endif /* _DEV_EXTRES_NVMEM_H_ */
+#endif /* _DEV_NVMEM_H_ */