sdcard_image-phy.bbclass: change name of partition volumes
sdcard_image-phy.bbclass: change name of partition volumes

Rename partition label to "boot" and "root" as default names are too
long.

Signed-off-by: Teresa Gámez <2d82cfe4bbaeb801b9ddb09534938e4b16a54218@phytec.de>
Signed-off-by: Stefan Müller-Klieser <a3e08e35e4a42be768e7d0e76ae1ba321c2a66dd@phytec.de>

PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec