amd-xgbe: TX Flow Ctrl Registers are h/w ver dependent

There is difference in the TX Flow Control registers (TFCR) between the
revisions of the hardware. The older revisions of hardware used to have
single register per queue. Whereas, the newer revision of hardware (from
ver 30H onwards) have one register per priority.

Update the driver to use the TFCR based on the reported version of the
hardware.

Fixes: c5aa9e3b

 ("amd-xgbe: Initial AMD 10GbE platform driver")
Co-developed-by: Ajith Nayak <Ajith.Nayak@amd.com>
Signed-off-by: Ajith Nayak <Ajith.Nayak@amd.com>
Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Acked-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>