media: cxd2880-spi: Fix an error handling path

If an error occurs after a successful 'regulator_enable()' call,
'regulator_disable()' must be called.

Fix the error handling path of the probe accordingly.

Fixes: cb496cd4 ("media: cxd2880-spi: Add optional vcc regulator")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>