media: atomisp: Add hmm_create_from_vmalloc_buf() function

Add a new hmm creating function to create a vmm object from a vmalloc-ed
kernel buffer. This is a preparation patch for adding videobuf2 (and
working MMAP mode) support.

Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>