.mailmap: update email address for Christopher Obbard

Update my email address.

Signed-off-by: Christopher Obbard <christopher.obbard@linaro.org>
diff --git a/.mailmap b/.mailmap
index 005e965..dc11775 100644
--- a/.mailmap
+++ b/.mailmap
@@ -36,6 +36,7 @@
 Boris Brezillon <bbrezillon@kernel.org> <boris.brezillon@bootlin.com>
 Boris Brezillon <bbrezillon@kernel.org> <boris.brezillon@free-electrons.com>
 Christian Kohn <chris.kohn@amd.com> <christian.kohn@xilinx.com>
+Christopher Obbard <christopher.obbard@linaro.org> <chris.obbard@collabora.com>
 Dirk Behme <dirk.behme@googlemail.com>
 Durga Challa <durga.challa@amd.com> <vnsl.durga.challa@xilinx.com>
 Eugen Hristev <eugen.hristev@linaro.org> <eugen.hristev@microchip.com>