arm64: defconfig: Make TEGRA186_GPC_DMA built-in

Make TEGRA186_GPC_DMA driver as built-in since the clients using the
DMA (like I2C_TEGRA etc) are built-in. This would avoid the potential
long delay probe deferral can cause.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>