ARM: shmobile: r8a7779: No TWD setup in C for Multiplatform

Skip the TWD setup in C for r8a7779 Multiplatform.
We should use DTS for the TWD device anyway.

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