test: linking test/compression.c fails

Building U-Boot with unit tests on a non-sandbox systems fails:

ld.bfd: test/built-in.o: in function `compress_using_gzip':
test/compression.c:138: undefined reference to `gzip'
ld.bfd: test/built-in.o: in function `uncompress_using_bzip2':
test/compression.c:187: undefined reference to `BZ2_bzBuffToBuffDecompress'
ld.bfd: test/built-in.o: in function `uncompress_using_lzma':
test/compression.c:222: undefined reference to `lzmaBuffToBuffDecompress'
ld.bfd: test/built-in.o: in function `uncompress_using_lzo':
test/compression.c:257: undefined reference to `lzop_decompress'
ld.bfd: test/built-in.o: in function `uncompress_using_lz4':
test/compression.c:292: undefined reference to `ulz4fn

Add the missing dependencies.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/Makefile b/test/Makefile
index 39ae04a..8296734 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -8,7 +8,7 @@
 obj-$(CONFIG_$(SPL_)CMDLINE) += cmd/
 obj-$(CONFIG_$(SPL_)CMDLINE) += cmd_ut.o
 obj-$(CONFIG_$(SPL_)CMDLINE) += command_ut.o
-obj-$(CONFIG_$(SPL_)CMDLINE) += compression.o
+obj-$(CONFIG_$(SPL_)UT_COMPRESSION) += compression.o
 obj-y += dm/
 obj-$(CONFIG_$(SPL_)CMDLINE) += print_ut.o
 obj-$(CONFIG_$(SPL_)CMDLINE) += str_ut.o