input: sensors: update adps993x binding documentation

Adps993x ambient light and proximity combo sensor driver is
compatible with adps993x series and adps990x series sensors,
binding documentation needs update to reflect this.

CRs-fixed 631108
Change-Id: I86a985fc993b105dbc3a2e38aa50031cf6a5be32
Signed-off-by: Bingzhe Cai <bingzhec@codeaurora.org>