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 bb7c82f13e7a01891edcdf0626c6fb91a240e56e and a proper
way to resolve the original issue was in
commit c04adbcd76725a360f411f09c63df785bf7db426. So, let's
remove the improper way AC_DEFINE(__state, state, ...).

Lustre-change: https://review.whamcloud.com/47799
Lustre-commit: f4c65e01a2e58b2bae770770590494d85ef636f7

Test-Parameters: trivial fstype=ldiskfs \
clientdistro=el8.6 serverdistro=el8.6 testlist=sanity

Test-Parameters: trivial fstype=zfs \
clientdistro=el8.6 serverdistro=el8.6 testlist=sanity

Change-Id: Icbc897cf5870352311262af8bd59ec24ea9d7301
Fixes: bb7c82f13e7 ("LU-15795 kernel: RHEL 8.6 server support")
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/47807
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>