MIPS: CPS: Fix MIPS_ISA_LEVEL_RAW fallout

Commit 17278a91 ("MIPS: CPS: Fix r1 .set mt assembler warning")
added .set MIPS_ISA_LEVEL_RAW to silence warnings about .set mt on r1,
however this can result in a MOVE being encoded as a 64-bit DADDU
instruction on certain version of binutils (e.g. 2.22), and reserved
instruction exceptions at runtime on 32-bit hardware.

Reduce the sizes of the push/pop sections to include only instructions
that are part of the MT ASE or which won't convert to 64-bit
instructions after .set mips64r2/mips64r6.
Reported-by: Greg Ungerer <gerg@linux-m68k.org>
Fixes: 17278a91 ("MIPS: CPS: Fix r1 .set mt assembler warning")
Signed-off-by: James Hogan <jhogan@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.15
Tested-by: Greg Ungerer <gerg@linux-m68k.org>
Patchwork: https://patchwork.linux-mips.org/patch/18578/

arch/mips/kernel/cps-vec.S

@@ -388,15 +388,16 @@ LEAF(mips_cps_boot_vpes)
 
 #elif defined(CONFIG_MIPS_MT)
 
-	.set	push
-	.set	MIPS_ISA_LEVEL_RAW
-	.set	mt
-
 	/* If the core doesn't support MT then return */
 	has_mt	t0, 5f
 
 	/* Enter VPE configuration state */
+	.set	push
+	.set	MIPS_ISA_LEVEL_RAW
+	.set	mt
 	dvpe
+	.set	pop
+
 	PTR_LA	t1, 1f
 	jr.hb	t1
 	 nop
@@ -422,6 +423,10 @@ LEAF(mips_cps_boot_vpes)
 	mtc0	t0, CP0_VPECONTROL
 	ehb
 
+	.set	push
+	.set	MIPS_ISA_LEVEL_RAW
+	.set	mt
+
 	/* Skip the VPE if its TC is not halted */
 	mftc0	t0, CP0_TCHALT
 	beqz	t0, 2f
@@ -495,6 +500,8 @@ LEAF(mips_cps_boot_vpes)
 	ehb
 	evpe
 
+	.set	pop
+
 	/* Check whether this VPE is meant to be running */
 	li	t0, 1
 	sll	t0, t0, a1
@@ -509,7 +516,7 @@ LEAF(mips_cps_boot_vpes)
 1:	jr.hb	t0
 	 nop
 
-2:	.set	pop
+2:
 
 #endif /* CONFIG_MIPS_MT_SMP */