xilinx: zynqmp: Allow multiboot environment write even in saved environment

xilinx: zynqmp: Allow multiboot environment write even in saved environment

Once the environment was saved, the current multiboot image information
became unreachable. When dealing with firmware updates, this information
is necessary alongside the saved environment to know the booted image.

Move the multiboot environment set operation before the saved environment
check to ensure this information is always available.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://lore.kernel.org/r/20240529100107.137159-1-kory.maincent@bootlin.com
Signed-off-by: Michal Simek <michal.simek@amd.com>