generic: 5.15: copy config and patch from 5.10

Copy config and patches from kernel 5.10 to kernel 5.15

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>

target/linux/generic/hack-5.15/261-lib-arc4-unhide.patch

@@ -0,0 +1,15 @@
+This makes it possible to select CONFIG_CRYPTO_LIB_ARC4 directly. We 
+need this to be able to compile this into the kernel and make use of it 
+from backports.
+
+--- a/lib/crypto/Kconfig
++++ b/lib/crypto/Kconfig
+@@ -6,7 +6,7 @@ config CRYPTO_LIB_AES
+ 	tristate
+ 
+ config CRYPTO_LIB_ARC4
+-	tristate
++	tristate "ARC4 cipher library"
+ 
+ config CRYPTO_ARCH_HAVE_LIB_BLAKE2S
+ 	tristate