Define CPUDIR for the .lds link script

Most link scripts differ only in the directory containing the start.o
file. Make this a #define to remove this last difference.

(Note that if start.o were disallowed outside the CPU start directory then
we wouldn't even need this. But that is a separate discussion.)

Signed-off-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -344,6 +344,7 @@ export PLATFORM_LIBS
 # on the fly.
 LDPPFLAGS += \
 	-include $(TOPDIR)/include/u-boot/u-boot.lds.h \
+	-DCPUDIR=$(CPUDIR) \
 	$(shell $(LD) --version | \
 	  sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')
 

spl/Makefile

@@ -93,6 +93,7 @@ endif
 LDPPFLAGS += \
 	-include $(TOPDIR)/include/u-boot/u-boot.lds.h \
 	-include $(OBJTREE)/include/config.h \
+	-DCPUDIR=$(CPUDIR) \
 	$(shell $(LD) --version | \
 	  sed -ne 's/GNU ld version \([0-9][0-9]*\)\.\([0-9][0-9]*\).*/-DLD_MAJOR=\1 -DLD_MINOR=\2/p')