projects/memtest: Fixup path to custom serdes place script

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>

projects/memtest/Makefile

@@ -18,7 +18,7 @@ DEVICE = up5k
 PACKAGE = sg48
 
 PIN_DEF = $(BUILD_TMP)/$(PROJ_TOP_MOD).pcf
-NEXTPNR_ARGS = --no-promote-globals --timing-allow-fail --pre-pack data/clocks.py --pre-place $(CORE_ice40_DIR)/sw/serdes-nextpnr-place.py
+NEXTPNR_ARGS = --no-promote-globals --timing-allow-fail --pre-pack data/clocks.py --pre-place $(CORE_no2ice40_DIR)/sw/serdes-nextpnr-place.py
 
 PCFS = $(abspath data/$(PROJ_TOP_MOD)-$(BOARD).pcf) $(abspath data/$(PROJ_TOP_MOD)-$(BOARD)-$(MEM).pcf)