USB: ssb: fix error handling in ssb_hcd_create_pdev()

This patch makes bcma_hcd_create_pdev() not return NULL, but a prober
error code in case of an error.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>