MIPS: MT: Remove SMTC support

Nobody is maintaining SMTC anymore and there also seems to be no userbase.
Which is a pity - the SMTC technology primarily developed by Kevin D.
Kissell <kevink@paralogos.com> is an ingenious demonstration for the MT
ASE's power and elegance.

Based on Markos Chandras <Markos.Chandras@imgtec.com> patch
https://patchwork.linux-mips.org/patch/6719/ which while very similar did
no longer apply cleanly when I tried to merge it plus some additional
post-SMTC cleanup - SMTC was a feature as tricky to remove as it was to
merge once upon a time.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/asmmacro.h

@@ -17,26 +17,8 @@
 #ifdef CONFIG_64BIT
 #include <asm/asmmacro-64.h>
 #endif
-#ifdef CONFIG_MIPS_MT_SMTC
-#include <asm/mipsmtregs.h>
-#endif
 
-#ifdef CONFIG_MIPS_MT_SMTC
-	.macro	local_irq_enable reg=t0
-	mfc0	\reg, CP0_TCSTATUS
-	ori	\reg, \reg, TCSTATUS_IXMT
-	xori	\reg, \reg, TCSTATUS_IXMT
-	mtc0	\reg, CP0_TCSTATUS
-	_ehb
-	.endm
-
-	.macro	local_irq_disable reg=t0
-	mfc0	\reg, CP0_TCSTATUS
-	ori	\reg, \reg, TCSTATUS_IXMT
-	mtc0	\reg, CP0_TCSTATUS
-	_ehb
-	.endm
-#elif defined(CONFIG_CPU_MIPSR2)
+#ifdef CONFIG_CPU_MIPSR2
 	.macro	local_irq_enable reg=t0
 	ei
 	irq_enable_hazard
@@ -71,7 +53,7 @@
 	sw      \reg, TI_PRE_COUNT($28)
 #endif
 	.endm
-#endif /* CONFIG_MIPS_MT_SMTC */
+#endif /* CONFIG_CPU_MIPSR2 */
 
 	.macro	fpu_save_16even thread tmp=t0
 	cfc1	\tmp, fcr31