staging: media: atomisp: fill properly hmm_bo_type_strings when ION is disabled

When CONFIG_ION is disabled, HMM_BO_LAST is 3. In this case, "i" should
not be added in hmm_bo_type_strings.

Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>