scripts: mkbootimg_rpi4.sh: Fix to install modules on non sudo

On sudo status, env variable is possible not to be preserved and
it causes failure on modules_install. So fix to install modules on
non sudo status and then move the directories and files to image
area.

[From repo of tizen rpi3: 89dcbe9b298c scripts: mkbootimg_rpi3.sh: Fix to install modules on non sudo status]
Change-Id: Ie7047c23762b668a08abf387dd76cf9cc8571937
Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>