msm: camera: Fix memory leak in cam_res_mgr_probe()

Since we have multiple CCIs with qcom,cam-res-mgr defined, the global
cam_res pointer gets overwritten each time a CCI probes, causing memory
to be leaked. Since it appears that the single global cam_res pointer is
intentional, let's just skip superfluous cam_res allocations to fix the
leak.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>