drivers: disk: add DISK_IOCTL_CTRL_INIT macro to initialize a disk

Add DISK_IOCTL_CTRL_INIT IOCTL to initialize a disk. This IOCTL is
intended to replace disk_access_init() for new applications, but
disk_access_init() is kept for legacy compatibility. The INIT IOCTL is
added to better match the path that will be used for disk
de-initialization. Like the disk_access_init() calls,
DISK_IOCTL_CTRL_INIT calls are reference counted

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>