Change mgr->available into mgr->used (invert the value).

Makes more sense to do it this way since we don't need the spinlock any
more to double check the handling.

v3 (chk): separated from the TEMPOARAY FLAG change.
Signed-off-by: NLang Yu <Lang.Yu@amd.com>
Signed-off-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAndrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: NNirmoy Das <nirmoy.das@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210622162339.761651-4-andrey.grodzovsky@amd.com