i2c: Use separate MODULE_AUTHOR() statements for multiple authors

Modules with multiple authors should use multiple MODULE_AUTHOR()
statements according to comment in include/linux/module.h.

Split the i2c modules with multiple authors to use multiple
MODULE_AUTHOR() statements.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>