ENGR00160834 UTP : replace kzalloc() with vmalloc()

ENGR00160834 UTP : replace kzalloc() with vmalloc()

When allocating large memory, such as 128K,
vmalloc() uses single page for the allocation process,
while kzalloc()	has to consume a continuous pages for the allocation.

In low memory case, the kzalloc() may fails.
So use the vmalloc() instead.

Also add some sanity check for the NULL pointer.

Signed-off-by: Huang Shijie <b32955@freescale.com>