MIPS: Use `FPU_CSR_ALL_X' in `__build_clear_fpe'

Replace a hardcoded numeric bitmask for FCSR cause bits with
`FPU_CSR_ALL_X' in `__build_clear_fpe'.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9684/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/genex.S

@@ -360,7 +360,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
 	.set	mips1
 	SET_HARDFLOAT
 	cfc1	a1, fcr31
-	li	a2, ~(0x3f << 12)
+	li	a2, ~FPU_CSR_ALL_X
 	and	a2, a1
 	ctc1	a2, fcr31
 	.set	pop