spi: cadence-quadspi: Implement refcount to handle unbind during busy

In the Linux kernel, the following vulnerability has been resolved: spi: cadence-quadspi: Implement refcount to handle unbind during busy driver support indirect read and indirect write operation with assumption no force device removal(unbind) operation. However force device removal(removal) is still available to root superuser. Unbinding driver during operation causes kernel crash. This changes ensure driver able to handle such operation for indirect read and indirect write by implementing refcount to track attached devices to the controller and gracefully wait and until attached devices remove operation completed before proceed with removal operation.