FMP: Remove GUIDs for FIT and raw images

The capsule update code has been modified for getting the image GUID
values from the platform code. With this, each image now has a unique
GUID value. With this change, there is no longer a need for defining
GUIDs for FIT and raw images. Remove these GUID values.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>