tests:image:check_p_rgb2greyscale_f32: Add support for Epiphany
tests:image:check_p_rgb2greyscale_f32: Add support for Epiphany

Signed-off-by: Ola Jeppsson <793f970c52ded1276b9264c742f19d1888cbaf73@adapteva.com>

debug-de-su-ka/pal,mateunho/pal,debug-de-su-ka/pal,debug-de-su-ka/pal,eliteraspberries/pal,eliteraspberries/pal,debug-de-su-ka/pal,parallella/pal,mateunho/pal,mateunho/pal,parallella/pal,debug-de-su-ka/pal,eliteraspberries/pal,eliteraspberries/pal,parallella/pal,parallella/pal,mateunho/pal,parallella/pal,aolofsson/pal,aolofsson/pal,aolofsson/pal,aolofsson/pal,eliteraspberries/pal,mateunho/pal