This commit add support for the yyets_le router.

Hardware Highlights:

SoC:	  Qualcomm IPQ4019 717 MHz
RAM:	  512M NT5CC256M16ER-EK
Flash:    32M SPI NOR MX25L25635F
WIFI1:    2.4 GHz 2T2R integrated
WIFI2:    5 GHz 2T2R integrated
Ethernet: Qualcomm QCA8075 (4x LAN, 1x WAN)
USB:      1x 3.0
LEDS:     power, wlan2g, wlan5g, usb
Button:   Reset

Installation:
 Upload the firmware on the upgrade page of the stcok, and this will
 take a few minutes.

This commit also supports the addition of a 128M nand flash version,
just use the P&W R619AC's OpBoot to overwrite the original uboot.
Signed-off-by: NAmadeusGhost <amadeus@jmu.edu.cn>