mpc83xx: Introduce ARCH_MPC837X

Replace CONFIG_MPC837x with a proper CONFIG_ARCH_MPC837X Kconfig option.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/arch/powerpc/include/asm/arch-mpc83xx/gpio.h b/arch/powerpc/include/asm/arch-mpc83xx/gpio.h
index 1699731..b5ec50b 100644
--- a/arch/powerpc/include/asm/arch-mpc83xx/gpio.h
+++ b/arch/powerpc/include/asm/arch-mpc83xx/gpio.h
@@ -9,7 +9,7 @@
 #if defined(CONFIG_ARCH_MPC8313) || defined(CONFIG_ARCH_MPC8308) || \
 	defined(CONFIG_ARCH_MPC8315)
 #define MPC83XX_GPIO_CTRLRS 1
-#elif defined(CONFIG_ARCH_MPC834X) || defined(CONFIG_MPC837x)
+#elif defined(CONFIG_ARCH_MPC834X) || defined(CONFIG_ARCH_MPC837X)
 #define MPC83XX_GPIO_CTRLRS 2
 #else
 #define MPC83XX_GPIO_CTRLRS 0