media: rkisp1: Fix wrong PHY config dependency

Instead of depending on the Rockchip PHY driver the ISP driver
should really depend on CONFIG_GENERIC_PHY_MIPI_DPHY,
given all it needs is the phy_mipi_dphy_get_default_config() symbol.

Fix it.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>