video: fix bug in cfb_console code

FILL_15BIT_555RGB macro extension for pixel swapping
by commit bed53753
introduced a bug in cfb_console:

Bitmaps with odd-numbered width won't be rendered
correctly and even U-Boot crashes are observed on
some platforms while repeated rendering of such
bitmaps with "bmp display". Also if a bitmap is
rendered to an odd-numbered x starting position,
the same problem occurs. This patch is an attempt
to fix it.

Signed-off-by: Anatolij Gustschin <agust@denx.de>