LU-4423 o2iblnd: use is_vmalloc_addr to check for vmalloc address

LU-4423 o2iblnd: use is_vmalloc_addr to check for vmalloc address

Instead of manually checking the bounds of VMALLOC_START and
VMALLOC_END, just use is_vmalloc_addr. That's what the function
was designed for.

Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Change-Id: Ic12fbac092305900d51f29569a079eea747cea34
Reviewed-on: http://review.whamcloud.com/8953
Tested-by: Jenkins
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>