Gowin. Divide packer. (YosysHQ#1645)

Split the packer into several files.

Signed-off-by: YRabbit <rabbit@yrabbit.cyou>

Author: yrabbit

himbaechel/uarch/gowin/CMakeLists.txt

@@ -13,6 +13,11 @@ set(SOURCES
     gowin_utils.cc
     gowin_utils.h
     pack.cc
+    pack_bsram.cc
+    pack_dsp.cc
+    pack_luts.cc
+    pack_io.cc
+    pack_iologic.cc
     pack.h
 )