EDAC, synopsys: Add error handling for the of_device_get_match_data() result

The function of_device_get_match_data() can return NULL in case of
error. Add error handling for the same in the mc_probe() function.

Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: Mauro Carvalho Chehab <mchehab@kernel.org>
CC: Michal Simek <michal.simek@xilinx.com>
CC: amit.kucheria@linaro.org
CC: devicetree@vger.kernel.org
CC: leoyang.li@nxp.com
CC: linux-arm-kernel@lists.infradead.org
CC: linux-edac <linux-edac@vger.kernel.org>
CC: mark.rutland@arm.com
CC: robh+dt@kernel.org
CC: sudeep.holla@arm.com
Link: http://lkml.kernel.org/r/1540447621-22870-2-git-send-email-manish.narani@xilinx.com