sdcard_image: fix sdcard image generation
sdcard_image: fix sdcard image generation

Rely on  shell environment when copying devicetree
and devicetree overlays to target image.

Signed-off-by: Janek Filus <99bbcfe6af9ca2902c4252f82daef1bdbd7cb1dd@bytesatwork.ch>
Signed-off-by: Khem Raj <729d64b6f67515e258459a5f6d20ec88b2caf8df@gmail.com>

d21d3q/meta-raspberrypi,schnitzeltony/meta-raspberrypi,leon-anavi/meta-raspberrypi,d21d3q/meta-raspberrypi,schnitzeltony/meta-raspberrypi,d21d3q/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,leon-anavi/meta-raspberrypi,agherzan/meta-raspberrypi,schnitzeltony/meta-raspberrypi,agherzan/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,kraj/meta-raspberrypi,d21d3q/meta-raspberrypi,LocutusOfBorg/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,agherzan/meta-raspberrypi,leon-anavi/meta-raspberrypi,kraj/meta-raspberrypi,agherzan/meta-raspberrypi,kraj/meta-raspberrypi