MAINTAINERS: rectify DELL WMI SYSMAN DRIVERS section

Commit e8a60aa7404b ("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 <[e-mail]>
Acked-by: Divya Bharathi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Hans de Goede <[e-mail]>

MAINTAINERS

···
 M:	Prasanth Ksr <[e-mail]>
 L:	[e-mail]
 S:	Maintained
-F:	drivers/platform/x86/dell-wmi-syman/*
+F:	Documentation/ABI/testing/sysfs-class-firmware-attributes
+F:	drivers/platform/x86/dell-wmi-sysman/
 
 DELL WMI NOTIFICATIONS DRIVER
 M:	Matthew Garrett <[e-mail]>