genalloc: fix allocation from end of pool

bitmap_find_next_zero_area requires the size of the bitmap, we instead
passed the last suitable position.  This made it impossible to allocate
from the end of the pool.

Fixes a regression introduced by 243797f59b748f679ab88d456fcc4f92236d724b
("genalloc: use bitmap_find_next_zero_area").

Signed-off-by: Imre Deak <imre.deak@nokia.com>
Cc: Zygo Blaxell <zygo.blaxell@xandros.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/genalloc.c

@@ -128,7 +128,6 @@ unsigned long gen_pool_alloc(struct gen_pool *pool, size_t size)
 		chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk);
 
 		end_bit = (chunk->end_addr - chunk->start_addr) >> order;
-		end_bit -= nbits + 1;
 
 		spin_lock_irqsave(&chunk->lock, flags);
 		start_bit = bitmap_find_next_zero_area(chunk->bits, end_bit, 0,