dt-bindings: mfd: ab8500: Remove weird Unicode characters

There are stray Unicode quotation marks (U+201C	DOUBLE TURNED COMMA
QUOTATION MARK) in the file. Remove them, as they don't serve a purpose.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>