agl_beaglebone.inc: remove old graphics preferences

agl_beaglebone.inc: remove old graphics preferences

Latest TI graphics completely redone its dependencies and preferences
to be aligned with upstream and use Mesa packages as proper providers
for GBM, EGL, GLES, etc. components. There's no more need for local
workarounds to adjust graphics settings.

Note: SGX is currently set in meta-ti-bsp to fall back to software
rendering and will be fixed later. Rogue in newer K3 devices is fully
functioning though.

Bug-AGL: SPEC-4723

Change-Id: Ifb6f594c6203924aa1b90f421d475b716c61a796
Signed-off-by: Denys Dmytriyenko <denys@konsulko.com>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/28743
Reviewed-by: Scott Murray <scott.murray@konsulko.com>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Tested-by: Jenkins Job builder account