feat(stm32mp1): add GUID's for identifying firmware images to be booted

Add GUID's for identifying the firmware image type. With the FWU
multi bank boot feature enabled, these GUID values are used to
identify the firmware image to be booted. This is done by matching
GUID values of images in the io policy table with the Image GUID value
that is read from the FWU metadata structure.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Change-Id: Id9751f02f95fc48ef68e4e3f9f0ddbf6d6319d3c