ARC: [plat-eznps] Fix TLB Errata

Due to a HW bug in NPS400 we get from time to time false TLB miss.
Workaround this by validating each miss.

Signed-off-by: Noam Camus <noamca@mellanox.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/mm/tlbex.S

@@ -274,6 +274,13 @@ ex_saved_reg1:
 .macro COMMIT_ENTRY_TO_MMU
 #if (CONFIG_ARC_MMU_VER < 4)
 
+#ifdef CONFIG_EZNPS_MTM_EXT
+	/* verify if entry for this vaddr+ASID already exists */
+	sr    TLBProbe, [ARC_REG_TLBCOMMAND]
+	lr    r0, [ARC_REG_TLBINDEX]
+	bbit0 r0, 31, 88f
+#endif
+
 	/* Get free TLB slot: Set = computed from vaddr, way = random */
 	sr  TLBGetIndex, [ARC_REG_TLBCOMMAND]
 
@@ -287,6 +294,8 @@ ex_saved_reg1:
 #else
 	sr TLBInsertEntry, [ARC_REG_TLBCOMMAND]
 #endif
+
+88:
 .endm