MIPS: DEC: Fix an int-handler.S CPU_DADDI_WORKAROUNDS regression

Fix a commit 3021773c ("MIPS: DEC: Avoid la pseudo-instruction in
delay slots") regression and remove assembly errors:

arch/mips/dec/int-handler.S: Assembler messages:
arch/mips/dec/int-handler.S:162: Error: Macro used $at after ".set noat"
arch/mips/dec/int-handler.S:163: Error: Macro used $at after ".set noat"
arch/mips/dec/int-handler.S:229: Error: Macro used $at after ".set noat"
arch/mips/dec/int-handler.S:230: Error: Macro used $at after ".set noat"

triggering with with the CPU_DADDI_WORKAROUNDS option set and the DADDIU
instruction.  This is because with that option in place the instruction
becomes a macro, which expands to an LI/DADDU (or actually ADDIU/DADDU)
sequence that uses $at as a temporary register.

With CPU_DADDI_WORKAROUNDS we only support `-msym32' compilation though,
and this is already enforced in arch/mips/Makefile, so choose the 32-bit
expansion variant for the supported configurations and then replace the
64-bit variant with #error just in case.

Fixes: 3021773c ("MIPS: DEC: Avoid la pseudo-instruction in delay slots")
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # 4.8+
Patchwork: https://patchwork.linux-mips.org/patch/16893/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/dec/int-handler.S

@@ -147,23 +147,12 @@
 		 * Find irq with highest priority
 		 */
 		# open coded PTR_LA t1, cpu_mask_nr_tbl
-#if (_MIPS_SZPTR == 32)
+#if defined(CONFIG_32BIT) || defined(KBUILD_64BIT_SYM32)
 		# open coded la t1, cpu_mask_nr_tbl
 		lui	t1, %hi(cpu_mask_nr_tbl)
 		addiu	t1, %lo(cpu_mask_nr_tbl)
-
-#endif
-#if (_MIPS_SZPTR == 64)
-		# open coded dla t1, cpu_mask_nr_tbl
-		.set	push
-		.set	noat
-		lui	t1, %highest(cpu_mask_nr_tbl)
-		lui	AT, %hi(cpu_mask_nr_tbl)
-		daddiu	t1, t1, %higher(cpu_mask_nr_tbl)
-		daddiu	AT, AT, %lo(cpu_mask_nr_tbl)
-		dsll	t1, 32
-		daddu	t1, t1, AT
-		.set	pop
+#else
+#error GCC `-msym32' option required for 64-bit DECstation builds
 #endif
 1:		lw	t2,(t1)
 		nop
@@ -214,23 +203,12 @@
 		 * Find irq with highest priority
 		 */
 		# open coded PTR_LA t1,asic_mask_nr_tbl
-#if (_MIPS_SZPTR == 32)
+#if defined(CONFIG_32BIT) || defined(KBUILD_64BIT_SYM32)
 		# open coded la t1, asic_mask_nr_tbl
 		lui	t1, %hi(asic_mask_nr_tbl)
 		addiu	t1, %lo(asic_mask_nr_tbl)
-
-#endif
-#if (_MIPS_SZPTR == 64)
-		# open coded dla t1, asic_mask_nr_tbl
-		.set	push
-		.set	noat
-		lui	t1, %highest(asic_mask_nr_tbl)
-		lui	AT, %hi(asic_mask_nr_tbl)
-		daddiu	t1, t1, %higher(asic_mask_nr_tbl)
-		daddiu	AT, AT, %lo(asic_mask_nr_tbl)
-		dsll	t1, 32
-		daddu	t1, t1, AT
-		.set	pop
+#else
+#error GCC `-msym32' option required for 64-bit DECstation builds
 #endif
 2:		lw	t2,(t1)
 		nop