drm/amdgpu: Fix missing unlocking in an error path in amdgpu_userq_create()

drm/amdgpu: Fix missing unlocking in an error path in amdgpu_userq_create()

If kasprintf() fails, some mutex still need to be released to avoid locking
issue, as already done in all other error handling path.

Fixes: c03ea34cbf88 ("drm/amdgpu: add support of debugfs for mqd information")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/all/366557fa7ca8173fd78c58336986ca56953369b9.1752087753.git.christophe.jaillet@wanadoo.fr/
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>