accel/amdxdna: Fix potential NULL pointer dereference in context cleanup

In the Linux kernel, the following vulnerability has been resolved: accel/amdxdna: Fix potential NULL pointer dereference in context cleanup aie_destroy_context() is invoked during error handling in aie2_create_context(). However, aie_destroy_context() assumes that the context's mailbox channel pointer is non-NULL. If mailbox channel creation fails, the pointer remains NULL and calling aie_destroy_context() can lead to a NULL pointer dereference. In aie2_create_context(), replace aie_destroy_context() with a function which request firmware to remove the context created previously.