drm/msm/sde: use constant size array in sde_watchdog_te_status

Prevent out of bounds access when using sde_watchdog_te_status
structure by using a constantly sized array definition. This
matches the usage convention in the rest of the sde_hw modules.

Change-Id: I44a94cc23a9d87e14ec7f6d1c28b36899cce11bb
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>