staging: iio: adc: lpc32xx: use correct reutrn value

To lpc32xx_adc driver, when platform_get_resource or
platform_get_irq failed, we should use -ENXIO as a
return value, but not -EBUSY.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald <pmeerw@pmeerw.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tapasweni Pathak <tapaswenipathak@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>