package/rtl8821au: fix license file name

Fixes #9976.

Reported-by: Nick Wright <nwright98@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rtl8821au/rtl8821au.mk

@@ -7,7 +7,7 @@
 RTL8821AU_VERSION = b018b446fb0729fa659e7eead475d6c13f192642
 RTL8821AU_SITE = $(call github,abperiasamy,rtl8812AU_8821AU_linux,$(RTL8821AU_VERSION))
 RTL8821AU_LICENSE = GPL-2.0
-RTL8821AU_LICENSE_FILES = COPYING
+RTL8821AU_LICENSE_FILES = LICENSE
 
 RTL8821AU_MODULE_MAKE_OPTS = \
 	CONFIG_RTL8812AU_8821AU=m \