Add Shawn McCarney as a reviewer

Shawn has experience on implementing fan control and I would like to add
him as a reviewer for more visibility to the current state and direction
openbmc phosphor-fan code is moving.

Change-Id: I4644e84d9c83e7af129dc0750a4af187864f05b4
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index a041f89..84092cf 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -45,3 +45,4 @@
 M:  Matthew Barth <msbarth@linux.ibm.com> <msbarth!>
 M:  Matt Spinler <spinler@us.ibm.com> <mspinler[m]!>
 R:  B.J. Wyman <bjwyman@gmail.com> <bjwyman!>
+R:  Shawn McCarney <shawnmm@us.ibm.com> <ShawnMcCarney[m]!>