drm/amdgpu/gfx: add generic handling for disable_kq

Add proper checks for disable_kq functionality in
gfx helper functions.  Add special logic for families
that require the clear state setup.

v2: use ring count as per Felix suggestion
v3: fix num_gfx_rings handling in amdgpu_gfx_graphics_queue_acquire()
v4: fix error code (Alex)

Reviewed-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Sunil Khatri <sunil.khatri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>