mtd: maps: Prepare merging of physmap and physmap_of

We want to merge the physmap and physmap_of driver, but before we can
do that we must prepare things to create physmap.o out of several .c
files. Rename physmap.c into physmap-core.c and add a new Makefile
rule to create physmap.o (right now it only contains physmap-core.o).

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

drivers/mtd/maps/Makefile

@@ -17,6 +17,8 @@ obj-$(CONFIG_MTD_ICHXROM)	+= ichxrom.o
 obj-$(CONFIG_MTD_CK804XROM)	+= ck804xrom.o
 obj-$(CONFIG_MTD_TSUNAMI)	+= tsunami_flash.o
 obj-$(CONFIG_MTD_PXA2XX)	+= pxa2xx-flash.o
+physmap-objs-y			+= physmap-core.o
+physmap-objs			:= $(physmap-objs-y)
 obj-$(CONFIG_MTD_PHYSMAP)	+= physmap.o
 physmap_of-objs-y		+= physmap_of_core.o
 physmap_of-objs-$(CONFIG_MTD_PHYSMAP_OF_VERSATILE) += physmap_of_versatile.o