MAINTAINERS: Karthikeyan Ramasubramanian is MIA

A mail just bounced back with "user unknown":

550 5.1.1 <kramasub@codeaurora.org> User doesn't exist

I also couldn't find a more recent address in git history. So, remove
this stale entry.
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

MAINTAINERS

@@ -13057,7 +13057,6 @@ F:	Documentation/devicetree/bindings/net/qcom,dwmac.txt
 
 QUALCOMM GENERIC INTERFACE I2C DRIVER
 M:	Alok Chauhan <alokc@codeaurora.org>
-M:	Karthikeyan Ramasubramanian <kramasub@codeaurora.org>
 L:	linux-i2c@vger.kernel.org
 L:	linux-arm-msm@vger.kernel.org
 S:	Supported