ARM: shmobile: r8a7794: Add IRQC clock to device tree

Link the external IRQ controller irqc0 to the IRQC module clock, so it
can be power managed using that clock.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

include/dt-bindings/clock/r8a7794-clock.h

@@ -60,6 +60,9 @@
 #define R8A7794_CLK_USBDMAC0		30
 #define R8A7794_CLK_USBDMAC1		31
 
+/* MSTP4 */
+#define R8A7794_CLK_IRQC		7
+
 /* MSTP5 */
 #define R8A7794_CLK_THERMAL		22
 #define R8A7794_CLK_PWM			23