[MIPS] pg-r4k.c: Fix a typo in an R4600 v2 erratum workaround

Restore a load from KSEG1 done as a workaround for an R4600 v2
erratum, dropped with 211be16de99a7424e66c0b6c0d00e2c970508ac2.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/mm/pg-r4k.c

@@ -209,7 +209,7 @@ static inline void build_cdex_p(void)
 	}
 
 	if (R4600_V2_HIT_CACHEOP_WAR && cpu_is_r4600_v2_x())
-		build_insn_word(0x3c01a000);	/* lui     $at, 0xa000  */
+		build_insn_word(0x8c200000);	/* lw      $zero, ($at) */
 
 	mi.c_format.opcode     = cache_op;
 	mi.c_format.rs         = 4;		/* $a0 */