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: "## To Build"]
```
Refer to markdown-lint [1] to fix MD041
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/041-first-line-h1.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I5238df966bd7a21b2217b2668fec2b95d3ed6ac9
diff --git a/README.md b/README.md
index ac8c657..1b9d67f 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,5 @@
+# phosphor-net-ipmid
+
 ## To Build
 
 ```