net: wwan: t7xx: Add control DMA interface

Cross Layer DMA (CLDMA) Hardware interface (HIF) enables the control
path of Host-Modem data transfers. CLDMA HIF layer provides a common
interface to the Port Layer.

CLDMA manages 8 independent RX/TX physical channels with data flow
control in HW queues. CLDMA uses ring buffers of General Packet
Descriptors (GPD) for TX/RX. GPDs can represent multiple or single
data buffers (DB).

CLDMA HIF initializes GPD rings, registers ISR handlers for CLDMA
interrupts, and initializes CLDMA HW registers.

CLDMA TX flow:
1. Port Layer write
2. Get DB address
3. Configure GPD
4. Triggering processing via HW register write

CLDMA RX flow:
1. CLDMA HW sends a RX "done" to host
2. Driver starts thread to safely read GPD
3. DB is sent to Port layer
4. Create a new buffer for GPD ring

Note: This patch does not enable compilation since it has dependencies
such as t7xx_pcie_mac_clear_int()/t7xx_pcie_mac_set_int() and
struct t7xx_pci_dev which are added by the core patch.

Signed-off-by: Haijun Liu <[email protected]>
Signed-off-by: Chandrashekar Devegowda <[email protected]>
Co-developed-by: Ricardo Martinez <[email protected]>
Signed-off-by: Ricardo Martinez <[email protected]>
Reviewed-by: Loic Poulain <[email protected]>
Reviewed-by: Ilpo Järvinen <[email protected]>
Reviewed-by: Sergey Ryazanov <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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