package/rauc: prevent occurring the error when directory exists
Add -p argument that ignore that specified directory already exists.
Fixes:
mkdir: cannot create directory ‘/home/bartekk/buildroot-2020.11-rc1/output/target/usr/lib/systemd/system/rauc.service.d’: File exists
Signed-off-by: Bartosz Bilas <b.bilas@grinn-global.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>