.editorconfig: set max line length to 100

Relax the 80 character line length, as done in checkpatch,
since Linux 5.7.

Change-Id: I093a2e6a45336339193173f7ff6a461279cf411d
Signed-off-by: Yann Gautier <yann.gautier@st.com>

.editorconfig

 #
-# Copyright (c) 2017-2019, Arm Limited and Contributors. All rights reserved.
+# Copyright (c) 2017-2020, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -38,10 +38,10 @@ indent_style = tab
 insert_final_newline = true
 
 # [LCS] Chapter 2: Breaking long lines and strings
-#       "The limit on the length of lines is 80 columns"
+#       "The limit on the length of lines is 100 columns"
 #   This is a "soft" requirement for Arm-TF, and should not be the sole
 #   reason for changes.
-max_line_length = 80
+max_line_length = 100
 
 # [LCS] Chapter 1: Indentation
 #       "Tabs are 8 characters"