drivers: remove octeontx2 drivers

drivers: remove octeontx2 drivers

As per the deprecation notice,  In the view of enabling unified driver
for octeontx2(cn9k)/octeontx3(cn10k), removing drivers/octeontx2
drivers and replace with drivers/cnxk/ which
supports both octeontx2(cn9k) and octeontx3(cn10k) SoCs.

This patch does the following

- Replace drivers/common/octeontx2/ with drivers/common/cnxk/
- Replace drivers/mempool/octeontx2/ with drivers/mempool/cnxk/
- Replace drivers/net/octeontx2/ with drivers/net/cnxk/
- Replace drivers/event/octeontx2/ with drivers/event/cnxk/
- Replace drivers/crypto/octeontx2/ with drivers/crypto/cnxk/
- Rename config/arm/arm64_octeontx2_linux_gcc as
  config/arm/arm64_cn9k_linux_gcc
- Update the documentation and MAINTAINERS to reflect the same.
- Change the reference to OCTEONTX2 as OCTEON 9. Old release notes and
the kernel related documentation is not accounted for this change.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Akhil Goyal <gakhil@marvell.com>
Acked-by: Ruifeng Wang <ruifeng.wang@arm.com>