Use the new tlb read hazard macros from <asm/hazards.h> rather than the
local BARRIER() macro which uses 7 ops regardless of the kernel
configuration.
We use mtc0_tlbr_hazard for the hazard between mtc0 to the index
register and the tlbr, and tlb_read_hazard for the hazard between the
tlbr and the mfc0 of the TLB registers written by tlbr.