init_shell: Add selinux permissions to access files and nodes

Allow init_shell script to set
- Entrypoint access needed to run shell scripts.
- Read write setattrs perms for dynamic_fps and bw_mode_bitmap nodes.
- Chown, fowner, fsetid perms for chown/chmod/mkdir.
- New prop added sf_lcd_density_prop used for setting DPI value.

Change-Id: I52c4ea5b7a6fc6dd9fa703a6780770fe66f814c5