ARM: shmobile: Enable VSP1 in shmobile_defconfig

Both r8a7790 and r8a7791 have multiple on-chip VSP1 devices, so
enable the VSP1 driver by default in the shmobile_defconfig.

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