ARM: OMAP: PM: Add more information on error path

Sometimes if some code tries to remove requested
throughput, the message "Invalid Device Structure"
is shown. This message is not informative because
it's unknown for what device it was tried - so
now added more information to that message.

Change-Id: Id26bf385dafd4992c8c3487d9dc38935e0fcd777
Signed-off-by: Ruslan Bilovol <ruslan.bilovol@ti.com>