drm: bridge: samsung-dsim: Select GENERIC_PHY_MIPI_DPHY

In order to support variable DPHY timings, it's necessary
to enable GENERIC_PHY_MIPI_DPHY so phy_mipi_dphy_get_default_config
can be used to determine the nominal values for a given resolution
and refresh rate.

Signed-off-by: Adam Ford <aford173@gmail.com>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230526030559.326566-5-aford173@gmail.com