rtl8821au: bump to 4c298b

Includes numerous stablity and cleanup passes by ulli-kroll.

A hash file is also added, as it was missing before.

Signed-off-by: Christian Stewart <christian@paral.in>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/rtl8821au/rtl8821au.hash

@@ -0,0 +1,2 @@
+# Locally calculated
+sha256 26e1a72b553a044ec34b57d9264ae7616c008a598a9009faba51331b55285a5b  rtl8821au-4c298b160253a7efa507c8ecdb868d1579ad02a7.tar.gz

package/rtl8821au/rtl8821au.mk

@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-RTL8821AU_VERSION = fef8c9d67d076eee9dfb9e19cb7cb69815d5a207
+RTL8821AU_VERSION = 4c298b160253a7efa507c8ecdb868d1579ad02a7
 RTL8821AU_SITE = $(call github,ulli-kroll,rtl8821au,$(RTL8821AU_VERSION))
 RTL8821AU_LICENSE = GPLv2, proprietary (rtl8821au.bin firmware)
 RTL8821AU_LICENSE_FILES = COPYING