Expand the specific configuration for the microblaze-generic
board in xparameters.h with a faked setup to enable the
LL_TEMAC driver.
Note: From now the microblaze-generic board is no longer a
valid board configuration for a real piece of hardware. Rather
than, we use the file config.mk and xparameters.h as a faked
board configuration to force the compilation of all potential
driver code for Microblaze systems.