IB/mthca: Clean up error unwind flow in mthca_reset()

The kfree() function was called in a few cases by the mthca_reset()
function during error handling even if the passed variables "bridge_header"
and "hca_header" contained a null pointer.

Adjust jump targets according to the Linux coding style convention.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>