mach-snapdragon: CapsuleUpdate: support all boot methods

mach-snapdragon: CapsuleUpdate: support all boot methods

Expand capsule update support to correctly identify which partition
U-Boot is flashed to (between xbl, uefi, and boot including A/B
variants).

Use qcom_boot_source to determine if we were chainloaded from ABL,
meaning U-Boot is on the boot partition, otherwise we assume uefi if
it's available, finally leaving the xbl partition.

Set a different fw_name based on the target partition to prevent GUID
collisions, since a board may support U-Boot flashed to boot or XBL we
need to differentiate them since the U-Boot binary must be built
differently.

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Link: https://lore.kernel.org/r/20250411-b4-qcom-capsule-update-improvements-v2-2-27f6b2fcc4a9@linaro.org
Signed-off-by: Casey Connolly <casey.connolly@linaro.org>