Update Manifest to rmeove unused dashboard files and include .c ethernet drivers (#4459)

MANIFEST.in

@@ -1,8 +1,6 @@
 include LICENSE
 include README.md
 include requirements.txt
-include esphome/dashboard/templates/*.html
-recursive-include esphome/dashboard/static *.ico *.js *.css *.woff* LICENSE
-recursive-include esphome *.cpp *.h *.tcc
+recursive-include esphome *.cpp *.h *.tcc *.c
 recursive-include esphome *.py.script
 recursive-include esphome LICENSE.txt