drm/amd/amdgpu: add missing mutex lock to amdgpu_get_xgmi_hive() (v3)

v2: Move locks around in other functions so that this
function can stand on its own.  Also only hold the hive
specific lock for add/remove device instead of the driver
global lock so you can't add/remove devices in parallel from
one hive.

v3: add reset_lock

Acked-by: Shaoyun.liu &lt; <Shaoyun.liu@amd.com>
Signed-off-by: Tom St Denis <tom.stdenis@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>