spi/bcm63xx: don't disable non enabled clocks in probe error path

When msg_ctl_width is set to an invalid value we try to disable the
clock despite it never being enabled. Fix it by jumping to the correct
label.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Acked-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>