remove redundant port/*/.gitignore; cleanup others

Author: dhalbert

ports/atmel-samd/.gitignore

@@ -1,9 +1,2 @@
-# Old Nordic soft devices that don't allow redistribution
-#########################################################
-drivers/bluetooth/s132_nrf52_2.0.1/
-
+# Softdevice .hex files that should be preserved
 !drivers/bluetooth/*/*.hex
-
-# Build files
-#####################
-build-*/

ports/cxd56/.gitignore

@@ -1,9 +1,3 @@
-# Build files
-#####################
-build-*/
-
 # Reference files
 #####################
 ref/
-
-.gdb_history

ports/litex/.gitignore

@@ -1,4 +1,3 @@
 micropython
 micropython-*
-*.py
 *.gcov