NTB: Rename ntb.c to support multiple source files in the module

The kbuild system does not support having multiple source files in
a module if one of those source files has the same name as the module.

Therefore, we must rename ntb.c to core.c, while the module remains
ntb.ko.

This is similar to the way the nvme modules are structured.

Signed-off-by: Logan Gunthorpe <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Allen Hubbe <[email protected]>
Signed-off-by: Jon Mason <[email protected]>

Author: lsgunth

drivers/ntb/Makefile

@@ -1,2 +1,4 @@
 obj-$(CONFIG_NTB) += ntb.o hw/ test/
 obj-$(CONFIG_NTB_TRANSPORT) += ntb_transport.o
+
+ntb-y := core.o