Hi, more info needed. You write nothing about what you did to compile module. Which kernel? Which sources? Which toolchain? And so on.
i2c_mux_* symbols are part of i2c-mux driver and these symbols are exported as GPL symbols. To use them you (1) need i2c-mux to be either compiled into the kernel or loaded as a module and (2) your m88ds3103 to be GPL licensed module so it can use GPL exported symbols.