config.mk: specify the exact path to standalone linker script

We want to change the build system to include config.mk
only from ./Makefile and spl/Makefile.
We must prepare for that in this commit.

$(src) is a moving target and not handy for our purpose.
We must replace it with a fixed path.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/mips/cpu/mips32/config.mk b/arch/mips/cpu/mips32/config.mk
index 7ee7faa..cd4ce7a 100644
--- a/arch/mips/cpu/mips32/config.mk
+++ b/arch/mips/cpu/mips32/config.mk
@@ -21,4 +21,5 @@
 PLATFORM_LDFLAGS  += -m elf32ltsmip
 endif
 
-CONFIG_STANDALONE_LOAD_ADDR ?= 0x80200000 -T $(srctree)/$(src)/mips.lds
+CONFIG_STANDALONE_LOAD_ADDR ?= 0x80200000 \
+			       -T $(srctree)/examples/standalone/mips.lds