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/ls1046ardb/README b/board/freescale/ls1046ardb/README
index a38c9d4..1660f7c 100644
--- a/board/freescale/ls1046ardb/README
+++ b/board/freescale/ls1046ardb/README
@@ -14,8 +14,8 @@
  LS1046ARDB board Overview
  -----------------------
  - SERDES1 Connections, 4 lanes supporting:
-      - Lane0: XFI with x1 RJ45 connector
-      - Lane1: XFI Cage
+      - Lane0: 10GBase-R with x1 RJ45 connector
+      - Lane1: 10GBase-R Cage
       - Lane2: SGMII.5
       - Lane3: SGMII.6
  - SERDES2 Connections, 4 lanes supporting: