rockchip: board: puma_rk3399: enable BMP_16BPP, BMP_24BPP and BMP_32BPP

With video output support for the RK3399-Q7 (Puma) available, we want
CMD_BMP enabled and the support for 16bit, 24bit and 32bit BMPs
defined.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

Version-changes: 2
- enable SYS_WHITE_ON_BLACK via defconfig
Reviewed-by: Simon Glass <sjg@chromium.org>