image_types_fsl.bbclass: Fix deploy of mxsboot-sdcard image
The mxsboot-sdcard image is the current way we use to generate the
U-Boot bootstream blob during image generation however Yocto image
system enforces some naming schema so the symbolic links does work and
we weren't following those. This patch uses the '${IMAGE_NAME}'
variable and the proper image suffix so the symbolic links now fully
work.
Fixes [YOCTO #3871].
Change-Id: I7f96dcdd58e0a726b8084c1f87ff10732fe259df Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
