modetest: add support for DRM_FORMAT_NV{15,20,30}

modetest: add support for DRM_FORMAT_NV{15,20,30}

Add smpte and tiles pattern for 10-bit NV15, NV20 and NV30 pixel formats
based on the existing pattern for NV12 with colors simply scaled from
8-bit to 10-bit.

These pixel formats are typically used by video decoder and display
pipeline on Rockchip SoCs, e.g. on RK322X, RK3288, RK3328 and RK3399
the video decoder produce 10-bit video frames in NV15 and NV20 format.

NV20 and NV30 pixel formats was added in drm-misc commit 728c15b4b5f3
("drm/fourcc: Add NV20 and NV30 YUV formats").

Changes in v2:

• Scale normal yuv 8-bit colors to 10-bit colors
• Add tiles test pattern

This can be tested/validated on Rockchip SoCs with drm-misc commit
d4b384228562 ("drm/rockchip: vop: Add NV15, NV20 and NV30 support")