android: binder: add missing return value documentation for binder_apply_fd_fixups()

android: binder: add missing return value documentation for binder_apply_fd_fixups()

The kernel-doc for binder_apply_fd_fixups() was missing a description of
its return value, which triggers a kernel-doc warning.

Add the missing "Return:" entry to doc that the function returns 0 on
success or a negative errno on failure.

Signed-off-by: Sunday Adelodun <adelodunolaoluwa@yahoo.com>
Link: https://patch.msgid.link/20251121111203.21800-2-adelodunolaoluwa@yahoo.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>