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/Kconfig b/arch/Kconfig
index c1b47b4..bad0352 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -34,6 +34,7 @@
 config MICROBLAZE
 	bool "MicroBlaze architecture"
 	select SUPPORT_OF_CONTROL
+	imply CMD_IRQ
 
 config MIPS
 	bool "MIPS architecture"
@@ -92,6 +93,7 @@
 	imply CMD_FPGA_LOADMK
 	imply CMD_GETTIME
 	imply CMD_IO
+	imply CMD_IRQ
 
 config XTENSA
 	bool "Xtensa architecture"