Net: rds: Makefile: Remove deprecated items

Changed Makefile to use <modules>-y instead of <modules>-objs
because -objs is deprecated and not mentioned in
Documentation/kbuild/makefiles.txt.

Also, use the ccflags-$ flag instead of EXTRA_CFLAGS because EXTRA_CFLAGS is
deprecated and should now be switched.

Last but not least, took out if-conditionals.

Signed-off-by: Tracey Dent <tdent48227@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>