ARM: shmobile: Select IRQC in case of the r8a7791 SoC

The r8a7791 contains IRQC hardware so make sure
the driver gets built by selecting RENESAS_IRQC.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>