ci-bridge-spi: Defer initialization of device and gpios

Defer initialization of the char device to be after driver
probing so that the device is not allocated if probing is
not performed or fails.

GPIOs configuration deferred to be done when device is
opened and not during probe so that the specific pins
are not used until the device is used by applications.

Change-Id: I4763e8d386300102a0ef4ed5467cac49593bd416
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>