LU-15973 build: remove AC_DEFINE(__state, state, ...)

LU-15973 build: remove AC_DEFINE(__state, state, ...)

RHEL 8.6 build failed with MLNX_OFED 5.6-2.0.9.0 as follows:

  error: 'struct task_struct' has no member named 'state';
  did you mean '__state'?
    #define __state state
                    ^~~~~

The failure was introduced by commit bb7c82f13e7a and a proper
way to resolve the original issue was in commit c04adbcd7672.
So, let's remove the improper way AC_DEFINE(__state, state, ...).

Lustre-change: https://review.whamcloud.com/47799
Lustre-commit: TBD (from 66c98e324b0182e781743cab4e938b18b6ef4255)

Test-Parameters: trivial clientdistro=el8.6 testlist=sanity
Fixes: bb7c82f13e7 ("LU-15795 kernel: RHEL 8.6 server support")
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Change-Id: Icbc897cf5870352311262af8bd59ec24ea9d7301
Reviewed-on: https://review.whamcloud.com/47804
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>