net: replace the "xfi" phy-mode with "10gbase-r"

As part of the effort of making U-Boot work with the same device tree as
Linux, there is an issue with the "xfi" phy-mode. To be precise, in
Linux there was a discussion (for those who have time to read:
https://lore.kernel.org/netdev/1576768881-24971-2-git-send-email-madalin.bucur@oss.nxp.com/)

which led to a patch:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=c114574ebfdf42f826776f717c8056a00fa94881

TL;DR: "xfi" was standardized in Linux as "10gbase-r".

This patch changes the relevant occurrences in U-Boot to use "10gbase-r"
instead of "xfi" wherever applicable.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/board/freescale/t208xrdb/README b/board/freescale/t208xrdb/README
index ec47c96..c4bfd3b 100644
--- a/board/freescale/t208xrdb/README
+++ b/board/freescale/t208xrdb/README
@@ -54,7 +54,7 @@
 T2080PCIe-RDB board Overview
 ----------------------------
  - SERDES Configuration
-     - SerDes-1 Lane A-B: to two 10G XFI fiber (MAC9 & MAC10)
+     - SerDes-1 Lane A-B: to two 10GBase-R fiber (MAC9 & MAC10)
      - SerDes-1 Lane C-D: to two 10G Base-T (MAC1 & MAC2)
      - SerDes-1 Lane E-H: to PCIe Goldfinger (PCIe4 x4, Gen3)
      - SerDes-2 Lane A-D: to PCIe Slot (PCIe1 x4, Gen2)
@@ -62,7 +62,7 @@
      - SerDes-2 Lane G-H: to SATA1 & SATA2
  - Ethernet
      - Two on-board 10M/100M/1G RGMII ethernet ports
-     - Two on-board 10Gbps XFI fiber ports
+     - Two on-board 10GBase-R fiber ports
      - Two on-board 10Gbps Base-T copper ports
  - DDR Memory
      - Supports 72bit 4GB DDR3-LP SODIMM