msm: camera: Add error check for msm_sd_register fail

This patch fixes a system crash by adding a proper error
handling in case msm_sd_register() has failed.

Without this new error handling, the caller will try to
access s_init->msm_sd.sd.devnode while it is null, which
leads to a crash.

Change-Id: I22009a1e5c8b6e12ff47106b0227e13ff046d86c
Signed-off-by: Maria Yu <aiquny@codeaurora.org>