Remove sdcard_image-rpi-gdp.bbclass

Remove sdcard_image-rpi-gdp.bbclass

Remove class sdcard_image-rpi-gdp. Historically it
was added during the initial porting of AGL to
Raspberry Pi and it had been taken from GENIVI
Development Platform. It is not needed anymore.

Bug-AGL: SPEC-409

Change-Id: I3f78b5fd92b08962c4a1fe07753627ae81da23ec
Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/9765
Reviewed-by: Matt Ranostay <matt.ranostay@konsulko.com>
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>