ola: Add patch to fix linking issue

This patch fixes this autobuild failure:

  http://autobuild.buildroot.net/results/e14/e14e1700d4fe359c56be57587bdb509e002e5753/build-end.log



The problem is caused by the -fvisibility-inlines-hidden switch.
Removing the switch is probably the least intrusive way we can make the
problem go away.  The first solution that was considered was to move the
definition of the offending method to the .cpp file.  However, with
other combinations of compilers and platforms, I suppose it could happen
with other methods as well.  Removing the switch ensures we catch them
all.

Built-tested with the config from the build bot, as well as with all OLA
options/plugins enabled.

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>