MAINTAINERS: remove section HISILICON STAGING DRIVERS FOR HIKEY 960/970

Commit 9bd9e0de ("mfd: hi6421-spmi-pmic: move driver from staging")
moves the last driver out of ./drivers/staging/hikey9xx/ and removes that
directory, but missed to adjust the HISILICON STAGING DRIVERS FOR HIKEY
960/970 section in MAINTAINERS.

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

  warning: no file matches    F:    drivers/staging/hikey9xx/

As the directory ./drivers/staging/hikey9xx/ is gone, remove the section
HISILICON STAGING DRIVERS FOR HIKEY 960/970 in MAINTAINERS as well.
Acked-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20210727093154.553-1-lukas.bulwahn@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -8440,11 +8440,6 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/mfd/hisilicon,hi6421-spmi-pmic.yaml
 F:	drivers/mfd/hi6421-spmi-pmic.c
 
-HISILICON STAGING DRIVERS FOR HIKEY 960/970
-M:	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
-S:	Maintained
-F:	drivers/staging/hikey9xx/
-
 HISILICON TRUE RANDOM NUMBER GENERATOR V2 SUPPORT
 M:	Zaibo Xu <xuzaibo@huawei.com>
 S:	Maintained