sdcard_image-rpi.bbclass: use 4 spaces for indentation instead of mix of tabs and spaces
sdcard_image-rpi.bbclass: use 4 spaces for indentation instead of mix of tabs and spaces

Signed-off-by: Martin Jansa <516df3ff67e1fa5d153800b15fb204c0a1a389dc@gmail.com>

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