drm/ttm: optimize pool allocations a bit v2

drm/ttm: optimize pool allocations a bit v2

[ Upstream commit 735c466465eba51deaee3012d8403c10fc7c8c03 ]

If we got a page pool use it as much as possible.

If we can't get more pages from the pool allocate as much as possible.

Only if that still doesn't work reduce the order and try again.

v2: minor cleanups

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221107195808.1873-1-christian.koenig@amd.com
Stable-dep-of: 379989e7cbdc ("drm/ttm/pool: Fix ttm_pool_alloc error path")
Signed-off-by: Sasha Levin <sashal@kernel.org>