platform_data: ad7793.h: drop a duplicated word

Drop the repeated word "and" in a comment.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>