powerpc: mpc8540: Remove macro CONFIG_MPC8540

Replace CONFIG_MPC8540 with ARCH_MPC8540 in Kconfig and clean up existing
macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/include/configs/MPC8540ADS.h b/include/configs/MPC8540ADS.h
index af3e85e..fab5a49 100644
--- a/include/configs/MPC8540ADS.h
+++ b/include/configs/MPC8540ADS.h
@@ -21,7 +21,6 @@
 /* High Level Configuration Options */
 #define CONFIG_BOOKE		1	/* BOOKE */
 #define CONFIG_E500		1	/* BOOKE e500 family */
-#define CONFIG_MPC8540		1	/* MPC8540 specific */
 #define CONFIG_MPC8540ADS	1	/* MPC8540ADS board specific */
 
 /*
diff --git a/include/keyboard.h b/include/keyboard.h
index 6725e48..e26f69e 100644
--- a/include/keyboard.h
+++ b/include/keyboard.h
@@ -98,7 +98,7 @@
 extern void pckbd_leds(unsigned char leds);
 #endif /* !CONFIG_DM_KEYBOARD */
 
-#if defined(CONFIG_MPC5xxx) || defined(CONFIG_MPC8540) || \
+#if defined(CONFIG_MPC5xxx) || defined(CONFIG_ARCH_MPC8540) || \
 		defined(CONFIG_MPC8541) || defined(CONFIG_MPC8555)
 int ps2ser_check(void);
 #endif