Move do_irqinfo() to common/cmd_irq.c

cmd_irq.c is a much better home and it is already conditionally
compiled based on CONFIG_CMD_IRQ.

Signed-off-by: Peter Tyser <ptyser@xes-inc.com>
diff --git a/common/cmd_irq.c b/common/cmd_irq.c
index 4604a5a..2c7e6bb 100644
--- a/common/cmd_irq.c
+++ b/common/cmd_irq.c
@@ -47,3 +47,12 @@
 	"enable or disable interrupts",
 	"[on, off]"
 );
+
+/* Implemented in $(CPU)/interrupts.c */
+int do_irqinfo (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+
+U_BOOT_CMD(
+	irqinfo,    1,    1,     do_irqinfo,
+	"print information about IRQs",
+	""
+);