swupdate-image: use image link name and autodetect FSTYPE
swupdate-image: use image link name and autodetect FSTYPE

Use IMAGE_LINK_NAME instead of IMAGE_BASENAME, but letting users to set
SWUPDATE_IMAGE_FSTYPES[$IMAGE_BASE_NAME] as usual.

Try to detect the extension for the image in case it is not seti by
iterating IMAGE_FSTYPES.

Signed-off-by: Stefano Babic <2c2905e0c2877c7e4ce40c7425e972302953fda5@denx.de>
CC: Adrian Freihofer <f98937d5b22471d73907edaa0389fa3148b095de@gmail.com>

sbabic/meta-swupdate,sbabic/meta-swupdate