resources: Remove execute permission for README files

This allows Gitiles to display README content for the folder
containing the file.

Signed-off-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
Change-Id: I433d0607dfbe990e1030b0d9e13bb544ef70b2d0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/36755
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/README.md b/README.md
old mode 100755
new mode 100644
diff --git a/src/boot-exit/README.md b/src/boot-exit/README.md
old mode 100755
new mode 100644
diff --git a/src/hack-back/README.md b/src/hack-back/README.md
old mode 100755
new mode 100644
diff --git a/src/npb/README.md b/src/npb/README.md
old mode 100755
new mode 100644