Use correct "D-Bus" spelling in README

Change "dbus" to the correct spelling "D-Bus".

Change-Id: Ic05a05751b8d79f76d207b17ba736057b68cac6b
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/README.md b/README.md
index 31d79e6..f485cee 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@
    OpenBMC
 
  - [dbus-interfaces.md](dbus-interfaces.md): Reference for APIs exposed
-   to dbus
+   to D-Bus
 
  - [kernel-development.md](kernel-development.md): Reference for common
    kernel development tasks