staging: vchiq: Refactor vchiq cdev code

Move the vchiq cdev initialization code to its own function for better
code organization. Call the initialization function during probe, thus
shifting the whole cdev creation logic (which was earlier split in
vchiq_probe() and vchiq_driver_init()) to vchiq_probe().

Reviewed-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Ojaswin Mujoo <ojaswin98@gmail.com>
Link: https://lore.kernel.org/r/c0e538eb0644292a52267d39edd85ab2af9f9a4e.1626882325.git.ojaswin98@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>