mm: save wasted memory by slab [1/1]

mm: save wasted memory by slab [1/1]

PD#SWPL-1767

Problem:
When driver/kernel call kmalloc with large size, memory may waste
if size is not equal to 2^n. For example, driver call kmalloc with
size 129KB, kmalloc will allocate a 256KB memory block to caller.
Then 127kb memory will be wasted if this caller don't free it.

Solution:
Free tail of slab memory if size is not match to 2^n. This change
can save about 900KB memory after boot, and more than 100KB during
run time.

Verify:
P212

Change-Id: Iba378792ec30003358b64384361c0f0c4c2800d8
Signed-off-by: tao zeng <tao.zeng@amlogic.com>