ARM: STMP3xxx: deallocation with negative index of descriptors[]

The last deallocation is invalid. In the last iteration, i is -1.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: dmitry pervushin <dpervushin@embeddedalley.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>