accel/amdxdna: Fix incorrect DPM level after suspend/resume

accel/amdxdna: Fix incorrect DPM level after suspend/resume

The suspend routine sets the DPM level to 0, which unintentionally
overwrites the previously saved DPM level. As a result, the device always
resumes with DPM level 0 instead of restoring the original value.

Fix this by ensuring the suspend path does not overwrite the saved DPM
level, allowing the correct DPM level to be restored during resume.

Fixes: f4d7b8a6bc8c ("accel/amdxdna: Enhance power management settings")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260204171048.3165580-1-lizhi.hou@amd.com