hwspinlock: Remove unused hwspin_lock_get_id()

hwspinlock: Remove unused hwspin_lock_get_id()

hwspin_lock_get_id() has been unused since the original 2011
commit bd9a4c7df256 ("drivers: hwspinlock: add framework")

Remove it and the corresponding docs.

Note that the of_hwspin_lock_get_id() version is still in use,
so leave that alone.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241215022023.181435-1-linux@treblig.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>