drm/amdgpu: Fix memory leak in amdgpu_ras_init()

In the Linux kernel, the following vulnerability has been resolved:

drm/amdgpu: Fix memory leak in amdgpu_ras_init()

When amdgpu_nbio_ras_sw_init() fails in amdgpu_ras_init(), the function

returns directly without freeing the allocated con structure, leading

to a memory leak.

Fix this by jumping to the release_con label to properly clean up the

allocated memory before returning the error code.

Compile tested only. Issue found using a prototype static analysis tool

and code review.