MIPS: TX49XX: use IS_ENABLED()

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3335/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mach-tx49xx/mangle-port.h

@@ -9,7 +9,7 @@
 #define ioswabb(a, x)		(x)
 #define __mem_ioswabb(a, x)	(x)
 #if defined(CONFIG_TOSHIBA_RBTX4939) && \
-	(defined(CONFIG_SMC91X) || defined(CONFIG_SMC91X_MODULE)) && \
+	IS_ENABLED(CONFIG_SMC91X) && \
 	defined(__BIG_ENDIAN)
 #define NEEDS_TXX9_IOSWABW
 extern u16 (*ioswabw)(volatile u16 *a, u16 x);