Add `YOSYS_` prefix to `DATA_DIR` and `PLUGINS_DIR` names.

Prepare for introduction of `PLUGIN_DIR` variable. `PLUGINS_DIR` could
be easily confused with the new variable.

Makefile_plugin.common

diff --git a/Makefile_plugin.common b/Makefile_plugin.common
index fd6d86e..a244a66 100644
--- a/Makefile_plugin.common
+++ b/Makefile_plugin.common
@@ -55,13 +55,13 @@
 LDLIBS := $(shell $(YOSYS_CONFIG) --ldlibs) $(LDLIBS)
 EXTRA_FLAGS ?=
 
-DATA_DIR = $(DESTDIR)$(shell $(YOSYS_CONFIG) --datdir)
-PLUGINS_DIR = $(DATA_DIR)/plugins
+YOSYS_DATA_DIR = $(DESTDIR)$(shell $(YOSYS_CONFIG) --datdir)
+YOSYS_PLUGINS_DIR = $(YOSYS_DATA_DIR)/plugins
 
 OBJS := $(patsubst %.cc,%.o,$(SOURCES))
 DEPS ?=
 
-$(PLUGINS_DIR):
+$(YOSYS_PLUGINS_DIR):
 	@mkdir -p $@
 
 all: $(NAME).so
@@ -75,8 +75,8 @@
 ../pmgen.py:
 	@$(MAKE) -C .. pmgen.py
 
-install_plugin: $(NAME).so | $(PLUGINS_DIR)
-	install -D $< $(PLUGINS_DIR)/$<
+install_plugin: $(NAME).so | $(YOSYS_PLUGINS_DIR)
+	install -D $< $(YOSYS_PLUGINS_DIR)/$<
 
 test:
 	@$(MAKE) -C tests all

dsp-ff-plugin/Makefile

diff --git a/dsp-ff-plugin/Makefile b/dsp-ff-plugin/Makefile
index 9cd9800..5eeb910 100644
--- a/dsp-ff-plugin/Makefile
+++ b/dsp-ff-plugin/Makefile
@@ -20,5 +20,5 @@
 include ../Makefile_plugin.common
 
 install:
-	install -D nexus-dsp_rules.txt $(DATA_DIR)/nexus/dsp_rules.txt
+	install -D nexus-dsp_rules.txt $(YOSYS_DATA_DIR)/nexus/dsp_rules.txt
 

ql-qlf-plugin/Makefile

diff --git a/ql-qlf-plugin/Makefile b/ql-qlf-plugin/Makefile
index 087a2b5..fd13bd5 100644
--- a/ql-qlf-plugin/Makefile
+++ b/ql-qlf-plugin/Makefile
@@ -96,7 +96,7 @@
 	python3 ../pmgen.py -o $@ -p ql_bram_asymmetric_wider_read ql-bram-asymmetric-wider-read.pmg
 
 install_modules: $(VERILOG_MODULES)
-	$(foreach f,$^,install -D $(f) $(DATA_DIR)/quicklogic/$(f);)
+	$(foreach f,$^,install -D $(f) $(YOSYS_DATA_DIR)/quicklogic/$(f);)
 
 install: install_modules
 

xdc-plugin/Makefile

diff --git a/xdc-plugin/Makefile b/xdc-plugin/Makefile
index 06d61d7..a81220b 100644
--- a/xdc-plugin/Makefile
+++ b/xdc-plugin/Makefile
@@ -20,6 +20,6 @@
 VERILOG_MODULES = BANK.v
 
 install_modules: $(VERILOG_MODULES)
-	install -D $< $(PLUGINS_DIR)/fasm_extra_modules/$<
+	install -D $< $(YOSYS_PLUGINS_DIR)/fasm_extra_modules/$<
 
 install: install_modules