gpu: nvgpu: gk20a: add fecs error intr handler

gpu: nvgpu: gk20a: add fecs error intr handler

Add handler gk20a_gr_handle_fecs_error() in case we have
pending fecs error interrupt
And clear this interrupt after handling.

Also, in gk20a_gr_handle_fecs_error(), for now just print
the contents of NV_PGRAPH_FECS_INTR and clear it

Bug 1495957

Change-Id: Ie7f70c84ec76ab698141646cd683584c4501e3e0
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/402874
(cherry picked from commit a29f219c57d65a06f6dae8086f19fa1af94d95bd)
Reviewed-on: http://git-master/r/403587
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>