lib/genalloc.c: use vzalloc_node() to allocate the bitmap

lib/genalloc.c: use vzalloc_node() to allocate the bitmap

Some devices may have big memory on chip, such as over 1G.  In some
cases, the nbytes maybe bigger then 4M which is the bounday of the
memory buddy system (4K default).

So use vzalloc_node() to allocate the bitmap.  Also use vfree to free
it.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Huang Shijie <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Alexey Skidanov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>