haven: hh_rm_core: Change datatype of num_fragments

Integer overflow can occur for a large value of req_buff_size because
num_fragments is declared as u8. Declare it as int in order to prevent
this from occurring.

Change-Id: I9e3655af13134ec57d123317ebb7b287a7470a19
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>