enable amdgpu on GCN1 and GCN2

# Enable amdgpu kernel driver for GCN 1 and GCN 2

mkdir -p /etc/default/grub.d

cat > /etc/default/grub.d/amdgpu_enable.cfg <<\EOF
# GCN1, HD 7970 and friends
GRUB_CMDLINE_LINUX_DEFAULT="${GRUB_CMDLINE_LINUX_DEFAULT} amdgpu.si_support=1 radeon.si_support=0"

# GCN2, R9 390X and friends
GRUB_CMDLINE_LINUX_DEFAULT="${GRUB_CMDLINE_LINUX_DEFAULT} amdgpu.cik_support=1 radeon.cik_support=0"
EOF

update-grub

# Don't forget to reboot!