LF-2512-1 ARM: imx_v6_v7_defconfig: enable CRYPTO_ARC4

Until recently, CONFIG_CRYPTO_ARC4 was selected by:
- HOSTAP [=y] && NETDEVICES [=y] && WLAN [=y] && WLAN_VENDOR_INTERSIL [=y]

However the series "[PATCH v3 0/7] crypto: mark ecb(arc4) skcipher as obsolete"
( https://lore.kernel.org/linux-crypto/20200831151649.21969-1-ardb@kernel.org/

 )
changed this, which means we must manually select the symbol.

Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Acked-by: Li Yang <leoyang.li@nxp.com>

arch/arm/configs/imx_v6_v7_defconfig

@@ -568,6 +568,7 @@ CONFIG_CRYPTO_SHA512=m
 CONFIG_CRYPTO_SHA3=m
 CONFIG_CRYPTO_TGR192=m
 CONFIG_CRYPTO_WP512=m
+CONFIG_CRYPTO_ARC4=m
 CONFIG_CRYPTO_BLOWFISH=m
 CONFIG_CRYPTO_CAMELLIA=m
 CONFIG_CRYPTO_CAST5=m