boards: shields: rk055hdmipi4ma0: Configure LVGL buffer for mimxrt700_evk Add LVGL display buffer configuration for the mimxrt700_evk board when using the rk055hdmipi4ma0 shield. Configure LVGL buffer section in SRAM1 with a 20% VDB size and disable full refresh mode to optimize memory usage and display performance. Signed-off-by: Kate Wang <yumeng.wang@nxp.com>