arm64 defconfig: enable MPT3 SAS and BNX2X drivers

ThunderX2 server requires both to provide storage and network.

05:00.0 Ethernet controller [0200]: Broadcom Limited BCM57840 NetXtreme II 10 Gigabit Ethernet [14e4:16a1] (rev 11)
05:00.1 Ethernet controller [0200]: Broadcom Limited BCM57840 NetXtreme II 10 Gigabit Ethernet [14e4:16a1] (rev 11)
8d:00.0 Serial Attached SCSI controller [0107]: LSI Logic / Symbios Logic SAS3224 PCI-Express Fusion-MPT SAS-3 [1000:00c4] (rev 01)

Signed-off-by: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>