NVMe: Rename nvme.c to nvme-core.c

In preparation for adding nvme-scsi.c
It is preferable to retain the module name 'nvme'
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

drivers/block/Makefile

@@ -42,4 +42,5 @@ obj-$(CONFIG_BLK_DEV_PCIESSD_MTIP32XX)	+= mtip32xx/
 
 obj-$(CONFIG_BLK_DEV_RSXX) += rsxx/
 
+nvme-y		:= nvme-core.o
 swim_mod-y	:= swim.o swim_asm.o