openrisc: move board linker script(s) to a common in cpu/

Unifies the openrisc boards linker scripts into a common one.

Signed-off-by: Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>

arch/openrisc/config.mk

@@ -25,3 +25,5 @@ CROSS_COMPILE ?= or32-elf-
 PLATFORM_CPPFLAGS += -DCONFIG_OPENRISC -D__OR1K__ -ffixed-r10
 
 CONFIG_STANDALONE_LOAD_ADDR ?= 0x40000
+
+LDSCRIPT ?= $(SRCTREE)/$(CPUDIR)/u-boot.lds