drm/imagination: Switch reset_reason fields from enum to u32

drm/imagination: Switch reset_reason fields from enum to u32

Update the reset_reason fwif structure fields from enum to u32 to remove
any ambiguity from the interface (enum is not a fixed size thus is unfit
for the purpose of the data type).

Fixes: a26f067feac1f ("drm/imagination: Add FWIF headers")
Signed-off-by: Alexandru Dadu <alexandru.dadu@imgtec.com>
Reviewed-by: Matt Coster <matt.coster@imgtec.com>
Link: https://patch.msgid.link/20260323-b4-firmware-context-reset-notification-handling-v3-2-1a66049a9a65@imgtec.com
Signed-off-by: Matt Coster <matt.coster@imgtec.com>