b43: only reload config after successful initialization

Commit 2a190322 (b43: reload phy and bss settings after core restarts)
introduced an unconditional call to b43_op_config() at the end of
b43_op_start(). When firmware fails to load this can wedge the system.
There's no need to reload the configuration after a failed
initialization anyway, so only make the call if initialization was
successful.

BugLink: http://bugs.launchpad.net/bugs/950295


Cc: Felix Fietkau <nbd@openwrt.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>