Add support for Asus RT-AC57U_V2

[dipol0]

Asking support for Asus RT-AC57U_V2

### Specifications

• CPU: Qualcomm QCN5502 WiSoC
  MIPS 74Kc (v5.0) @775MHz
• WLAN: Qualcomm QCN5502/QCA9888
  802.11n 2T2R (300Mbps, 2.4GHz)
  802.11ac 2T2R (867Mbps, 5GHz)
• USB: 1x USB 2.0 ports

Original Asus rt-ac57u_v2 firmware based on OpenWrt/LEDE but to old (kernel 3.3.x)
Latest FW - v 3.0.0.4.382.52107 2020/02/24

**Source Code**
Версия 3.0.0.4.382.52107 2020/03/12 - 484.7 MBytes
[GPL of ASUS RT-AC57U V2 for firmware 3.0.0.4.382.52107]

Download source - https://dlcdnets.asus.com/pub/ASUS/wireless/RT-AC57U_V2/GPL_RT_AC57U_V2_300438252107.zip

Asus RT-AC57U_V2 information on wikidevi.wi-cat.ru

I think it similar as RT-AC59U (hardware):

#cat /proc/cpuinfo
system type : Qualcomm Atheros QCA5502 rev 0
machine : Qualcomm Atheros APJET01 reference board
processor : 0
cpu model : MIPS 74Kc V5.0
BogoMIPS : 385.84
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0000, 0x0710, 0x0958, 0x07f0]
ASEs implemented : mips16 dsp
shadow register sets : 1
kscratch registers : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available

#uname -a
Linux RT-AC57U_V2 3.3.8 #1 Sat Feb 8 04:00:28 CST 2020 mips GNU/Linux

[alex.const]

Hello @dipol0 ! Thank you for the information you provided! Could we continue this discussion in another thread on the same topic? See Support for RT-AC57U v2