kbuild: delete redundant LDSCRIPT definition

$(SRCTREE)/$(CPUDIR)/u-boot.lds is our default location
of arch-specific linker script.

Remove redundant definitions in
arch/{arc,microblaze,openrisc}/config.mk.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Cc: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
Acked-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/arc/config.mk b/arch/arc/config.mk
index d9f5d9d..a3b8df7 100644
--- a/arch/arc/config.mk
+++ b/arch/arc/config.mk
@@ -23,8 +23,6 @@
 
 PLATFORM_CPPFLAGS += -ffixed-r25 -D__ARC__ -DCONFIG_ARC -gdwarf-2
 
-LDSCRIPT := $(SRCTREE)/$(CPUDIR)/u-boot.lds
-
 # Needed for relocation
 LDFLAGS_FINAL += -pie
 
diff --git a/arch/microblaze/config.mk b/arch/microblaze/config.mk
index cdb321a..98bbf79 100644
--- a/arch/microblaze/config.mk
+++ b/arch/microblaze/config.mk
@@ -15,5 +15,3 @@
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x80F00000
 
 PLATFORM_CPPFLAGS += -ffixed-r31 -D__microblaze__
-
-LDSCRIPT ?= $(SRCTREE)/$(CPUDIR)/u-boot.lds
diff --git a/arch/openrisc/config.mk b/arch/openrisc/config.mk
index 981edff..9902b9a 100644
--- a/arch/openrisc/config.mk
+++ b/arch/openrisc/config.mk
@@ -14,5 +14,3 @@
 PLATFORM_CPPFLAGS += -DCONFIG_OPENRISC -D__OR1K__ -ffixed-r10
 
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x40000
-
-LDSCRIPT ?= $(SRCTREE)/$(CPUDIR)/u-boot.lds