scsi: ufs: Fix back to back clk gate work

In some rare scenario, inconsistent state b/w
clk_gating.state and uic link state is observed
when back to back clk_gate_work gets scheduled.

Sequence of events:
1. hibern8 enter fails as a part of ufshc_gate_work.

2. Link recovery marks eh_in_progress and schedules
   the error handler to recovery the failure.

3. Error handler finished its work, it
   clears eh_in_progress and returns, thus link recovery
   succeeds

4. THe next retry of hibern8 succeed and sets the
   clk_gating.state to CLK_OFF.

5. B/w step 2 and 4 when eh_in_progress is already set,
   if any async thread says IOCTL calls ufshcd_hold, only
   clk_gating.active_requests increases and it bails out.

6. After async thread finishes its job and calls ufshcd_release.
   if ufshcd_release() is called after eh_in_progress is
   cleared, it would schedule  the
   clk_gate_work instead of bailing out.

7. when 2nd gate_work runs after 1st clk gate work is over,
   since 1st gate work would have set the clk_gating.state
   as CLKS_OFF, the current gate work sets
   clk_gating.state to CLKS_ON and bails out.
   This leaves the clk_gating.state as CLKS_ON and link as
   hibern8 state which causes inconsistency and causes i/o block
   and deadloop when new i/o request calls ufshcd_hold functions
   with sync flag as false and true successfully.

Fix this by checking clk_gating.state, if it is already CLKS_OFF,
bail from clk_gate_work().

Change-Id: Ia60a4c872c39636c1e5144584025f8938e712202
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Nitin Rawat <nitirawa@codeaurora.org>