ramips: fix wrong permissions on dts files
This commit fixes wrong permissions on dts files. Before the commit these
dts files are executable:
-rwxrwxr-x mt7620a_dlink_dir-806a-b1.dts
-rwxrwxr-x mt7621_wavlink_wl-wn573hx1.dts
Signed-off-by: Mikhail Zhilkin <[email protected]>