ARM: shmobile: No need to use INTC demux on r8a7740

Now when the r8a7740 code has been converted to make use of
GIC instead of INTC for root interrupt controller it is
possible to exclude the low level INTC demux function
shmobile_handle_irq_intc from linking.

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