FROMGIT: scsi/scsi_error: Use call_rcu_flush() instead of call_rcu()

Slow boot time is seen on KVM running typical Linux distributions due to
SCSI layer calling call_rcu(). Recent changes to save power may be
causing this slowness. Using call_rcu_flush() fixes the issue and brings
the boot time back to what it originally was. Convert it.

(cherry picked from commit 716cac6652c8512ba939a7f62eada6589d9c84d6
 https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

 rcu/next)

BUG=b:222463781
TEST=powerIdle lab tests.

Tested-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes <joelaf@google.com>
Signed-off-by: Parshuram Sangle <parshuram.sangle@intel.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3965076


Reviewed-by: Ross Zwisler <zwisler@google.com>
Change-Id: I968164f96008e23e5d249ccd99224a1feca2a38c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/4069545