doc: postpone ABI changes in igb_uio

doc: postpone ABI changes in igb_uio

This ABI changes to remove iomem and ioport mapping in igb_uio. The
purpose of this changes was to fix a bug: when DPDK app crashes,
those devices by igb_uio are not stopped either DPDK PMD driver or
igb_uio driver.

Then it has been pointed out by Stephen Hemminger that it has
backward compatibility issue: cannot run old version DPDK on
modified igb_uio.

However, we still have not figure out a new way to fix this bug
without this change. Let's postpone this deprecation announcement
in case this change cannot be avoided.

Fixes: 3bac1dbc1ed ("doc: announce iomem and ioport removal from igb_uio")

Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
Suggested-by: Ferruh Yigit <ferruh.yigit@intel.com>
Suggested-by: Thomas Monjalon <thomas.monjalon@6wind.com>
Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>