Add Mini PCIe slot TE 2041626

Add Mini PCIe mounting holes and board mounting holes
Add nano SIM card slot SIM8066
Add SIM ESD and EMI filter EMIF03-SIM02M8
Add USB Hub USB2422
Add USB A port with ESD chip
Add README.md for details about HLK-7628N
Edit text above ethernet ports

doc/hardware/hlk7628/README.md

@@ -0,0 +1,5 @@
+### Default UART baud rate
+The default baud rate is: 57600 baud
+
+### Flash OpenWRT via UART
+