Fix bad links in the documentation

doc/modbus_read_input_bits.txt

@@ -38,7 +38,7 @@ Too many discrete inputs requested
 
 SEE ALSO
 --------
-linkmb:modbus_write_input_bits[3]
+linkmb:modbus_read_input_registers[3]
 
 
 AUTHORS

doc/modbus_read_input_registers.txt

@@ -40,8 +40,9 @@ Too many bits requested
 
 SEE ALSO
 --------
-linkmb:modbus_read_[3]
-linkmb:modbus_write_bit[3]
+linkmb:modbus_read_input_bits[3]
+linkmb:modbus_write_register[3]
+linkmb:modbus_write_registers[3]
 
 
 AUTHORS

doc/modbus_write_register.txt

@@ -28,7 +28,7 @@ it shall return -1 and set errno.
 
 SEE ALSO
 --------
-linkmb:modbus_read_register[3]
+linkmb:modbus_read_registers[3]
 linkmb:modbus_write_registers[3]
 
 

doc/modbus_write_registers.txt

@@ -29,8 +29,8 @@ registers if successful. Otherwise it shall return -1 and set errno.
 
 SEE ALSO
 --------
-linkmb:modbus_read_register[3]
 linkmb:modbus_write_register[3]
+linkmb:modbus_read_registers[3]
 
 
 AUTHORS