video: bmp: Fix video_display_rle8_bitmap()

In case the BMP size is bigger than the frame buffer, don't use
the BMP's width and height in video_display_rle8_bitmap, but the
one's checked in video_bmp_display() as parameters to
video_display_rle8_bitmap().

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
CC: Yannick Fertré <yannick.fertre@st.com>