MAINTAINERS: rectify DELL WMI SYSMAN DRIVERS section

Commit e8a60aa7 ("platform/x86: Introduce support for Systems
Management Driver over WMI for Dell Systems") added a new section
DELL WMI SYSMAN DRIVERS in MAINTAINERS, but slipped in a typo.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches    F:    drivers/platform/x86/dell-wmi-syman/*

Point the file entry to the right location and add an entry for its
Documentation while at it.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Divya Bharathi <divya.bharathi@dell.com>
Link: https://lore.kernel.org/r/20201029114425.22520-1-lukas.bulwahn@gmail.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>