[ARM] Remove MT_DEVICE_IXP2000 and associated definitions

As of the previous commit, MT_DEVICE_IXP2000 encodes to the same
PTE bit encoding as MT_DEVICE, so it's now redundant.  Convert
MT_DEVICE_IXP2000 to use MT_DEVICE instead, and remove its aliases.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/proc-xscale.S b/arch/arm/mm/proc-xscale.S
index 534b4be..01adbd9 100644
--- a/arch/arm/mm/proc-xscale.S
+++ b/arch/arm/mm/proc-xscale.S
@@ -443,7 +443,7 @@
 	.long	0x00						@ unused
 	.long	PTE_CACHEABLE | PTE_BUFFERABLE			@ L_PTE_MT_DEV_CACHED
 	.long	0x00						@ L_PTE_MT_DEV_NONSHARED
-	.long	PTE_EXT_TEX(1) | PTE_BUFFERABLE			@ L_PTE_MT_DEV_IXP2000
+	.long	0x00						@ unused
 	.long	0x00						@ unused
 	.long	0x00						@ unused