kbuild: remove unnecessary "obj- := dummy.o" trick

In these Makefiles, at least one of "obj-y" and "obj-" is non-empty,
hence built-in.o is always created without such a trick.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Peter Foley <pefoley2@pefoley.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Acked-by: Simon Horman <horms+renesas@verge.net.au> [shmobile]
Acked-by: David S. Miller <davem@davemloft.net> [networking]
Signed-off-by: Michal Marek <mmarek@suse.cz>

arch/arm/plat-samsung/Makefile

@@ -8,7 +8,6 @@ ccflags-$(CONFIG_ARCH_MULTI_V7) += -I$(srctree)/$(src)/include
 
 obj-y				:=
 obj-m				:=
-obj-n				:= dummy.o
 obj-				:=
 
 # Objects we always build independent of SoC choice

drivers/clk/shmobile/Makefile

@@ -6,5 +6,3 @@ obj-$(CONFIG_ARCH_R8A7790)		+= clk-rcar-gen2.o
 obj-$(CONFIG_ARCH_R8A7791)		+= clk-rcar-gen2.o
 obj-$(CONFIG_ARCH_SHMOBILE_MULTI)	+= clk-div6.o
 obj-$(CONFIG_ARCH_SHMOBILE_MULTI)	+= clk-mstp.o
-# for emply built-in.o
-obj-n	:= dummy

drivers/net/wimax/Makefile

@@ -1,5 +1 @@
-
 obj-$(CONFIG_WIMAX_I2400M)	+= i2400m/
-
-# (from Sam Ravnborg) force kbuild to create built-in.o
-obj- := dummy.o