i2c: designware: constify abort_sources

We never modify abort_sources, mark it as const.

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>