README.md: Fix MD041 warnings

The following warnings are generated by using markdownlint analysis:
```
MD041/first-line-heading/first-line-h1 First line in a file should be a top-level heading [Context: "### Ethernet Statistics Command..."]
```
Refer to markdown-lint [1] to fix MD041
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/041-first-line-h1.md

Change-Id: I11b661fb02b389d40e3d037203138b534d54b27d
Signed-off-by: George Liu <liuxiwei@ieisystem.com>
diff --git a/README.md b/README.md
index 3198358..e3fb440 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-### Ethernet Statistics Command (0x30)
+# Ethernet Statistics Command (0x30)
 
 There is the need to read a specific ethernet-level statistic value from the
 BMC. This is driven primarily to detect link errors that require hardware swaps