Convert CONFIG_CMD_IRQ to Kconfig

This converts the following to Kconfig:
   CONFIG_CMD_IRQ

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index eae94c8..f37a9cb 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -34,6 +34,7 @@
 	select SYS_FSL_DDR_BE
 	imply USB_EHCI_HCD if USB
 	imply CMD_HASH
+	imply CMD_IRQ
 
 config MPC86xx
 	bool "MPC86xx"
@@ -46,6 +47,7 @@
 config 4xx
 	bool "PPC4xx"
 	select CREATE_ARCH_SYMLINK
+	imply CMD_IRQ
 
 endchoice
 
diff --git a/arch/powerpc/cpu/mpc5xxx/Kconfig b/arch/powerpc/cpu/mpc5xxx/Kconfig
index 5d49228..6ba0dd4 100644
--- a/arch/powerpc/cpu/mpc5xxx/Kconfig
+++ b/arch/powerpc/cpu/mpc5xxx/Kconfig
@@ -59,6 +59,7 @@
 
 config TARGET_DIGSY_MTC
 	bool "Support digsy_mtc"
+	imply CMD_IRQ
 
 config TARGET_PCM030
 	bool "Support pcm030"
diff --git a/arch/powerpc/cpu/mpc83xx/Kconfig b/arch/powerpc/cpu/mpc83xx/Kconfig
index 02e43bc..0772b7c 100644
--- a/arch/powerpc/cpu/mpc83xx/Kconfig
+++ b/arch/powerpc/cpu/mpc83xx/Kconfig
@@ -49,6 +49,7 @@
 
 config TARGET_MPC8349ITX
 	bool "Support MPC8349ITX"
+	imply CMD_IRQ
 
 config TARGET_MPC837XEMDS
 	bool "Support MPC837XEMDS"