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/configs/xpedite537x_defconfig b/configs/xpedite537x_defconfig
index 07fdfaf..45fe128 100644
--- a/configs/xpedite537x_defconfig
+++ b/configs/xpedite537x_defconfig
@@ -19,6 +19,7 @@
 CONFIG_CMD_DATE=y
 # CONFIG_CMD_HASH is not set
 CONFIG_CMD_JFFS2=y
+# CONFIG_CMD_IRQ is not set
 CONFIG_SYS_FSL_DDR2=y
 CONFIG_DS4510=y
 # CONFIG_MMC is not set