phy: Select PHY_EXYNOS_MIPI_VIDEO by default for ARCH_EXYNOS

Instead of requiring user to figure out when PHY_EXYNOS_MIPI_VIDEO needs
to be selected select it by default for Exynos SoCs. Also enable it when
COMPILE_TEST is selected. If required the MIPI CSIS/DPHY driver can be
then disabled or compiled in as module.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>