editorconfig: Set insert_final_newline true

This is what checkpatch.pl expects, and GitHub's file viewer flags a
missing trailing newline too.

Note that this is different from a blank line at the end of the file. It
just says whether the last line must end in a newline.

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>

.editorconfig

@@ -7,7 +7,7 @@ root = true
 [*]
 charset = utf-8
 end_of_line = lf
-insert_final_newline = false
+insert_final_newline = true
 trim_trailing_whitespace = true
 
 # C
@@ -53,4 +53,4 @@ indent_size = 2
 
 # Makefile
 [Makefile]
-indent_style = tab
+indent_style = tab