driver:base:core: Adding a "Return:" line in comment for device_link_add()

The original document doesn't explain the return value directly which
leads to confusing in error checking.

You can find the reason here:
Link: https://lore.kernel.org/all/1d4c39e109bcf288d5900670e024a315.sboyd@kernel.org/



Signed-off-by: Yuesong Li <liyuesong@vivo.com>
Link: https://lore.kernel.org/r/20240821040432.4049183-1-liyuesong@vivo.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>